Epidermal growth factor receptor kinase substrate (EPS8)-like Phosphotyrosine-binding (PTB) domain; EPS8 is a regulator of Rac signaling. It consists of a PTB and an SH3 domain. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains. This cd is part of the Dab-like subgroup.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2023551189   48 ETSQYHVQHLATFIMDKSEAIATVDDAIRKLVQLSSKEKVWAQEMLLQVNDQSLRLLDVESQvwqrqgsrgregspnrdp 127
Cdd:cd01210      1 DTSQYRVEHLATFTLGREEGVQTVEDALRKLKELDAKGRIWSQEMLLQVNDGWVLLLDIETK------------------ 62

                           90       100       110       120       130       140       150       160
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2023551189  128 dtqlglsagagqdeegkgqagqeglrrarlcpsrgdclaesrsasaprpcrayqlwlcprhtahrpgsrvtptalsvaqv 207
Cdd:cd01210        --------------------------------------------------------------------------------

                          170       180       190       200       210       220       230
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 2023551189  208 qpapvaEELENFPLPTVRHSQTVLNQLRYPSVLLLVCQDSEQSKPDIHFFHCDEVEAELVHEDIESALADCRLGK 282
Cdd:cd01210     63 ------EELESFPLSSIQECTAVLSTCSYNSILLLVVQEPDQPKPEMHLFQCDEVGAELLVEDLQKALSGKRSGR 131

Src Homology 3 domain of Epidermal growth factor receptor kinase substrate 8 and similar proteins; This group is composed of Eps8 and Eps8-like proteins including Eps8-like 1-3, among others. These proteins contain N-terminal Phosphotyrosine-binding (PTB), central SH3, and C-terminal effector domains. Eps8 binds either Abi1 (also called E3b1) or Rab5 GTPase activating protein RN-tre through its SH3 domain. With Abi1 and Sos1, it becomes part of a trimeric complex that is required to activate Rac. Together with RN-tre, it inhibits the internalization of EGFR. The SH3 domains of Eps8 and similar proteins recognize peptides containing a PxxDY motif, instead of the classical PxxP motif. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 2023551189  907 YVRILYDFTARNANELSVLKDEVLEVLEDGHQWWKVRNRSGQAGYVPCNILD 958
Cdd:cd11764      1 YVRVLYDFTARNSKELSVLKGEYLEVLDDSRQWWKVRNSRGQVGYVPHNILE 52

SAM (Sterile alpha motif ); SAM (Sterile Alpha Motif) domain is a module consisting of approximately 70 amino acids. This domain is found in the Fungi/Metazoa group and in a restricted number of bacteria. Proteins with SAM domains are represented by a wide variety of domain architectures and have different intracellular localization, including nucleus, cytoplasm and membranes. SAM domains have diverse functions. They can interact with proteins, RNAs and membrane lipids, contain site of phosphorylation and/or kinase docking site, and play a role in protein homo and hetero dimerization/oligomerization in processes ranging from signal transduction to regulation of transcription. Mutations in SAM domains have been linked to several diseases.

                           10        20
                   ....*....|....*....|
gi 2023551189 1032 PLTYESGPEEVRAWLEAKAF 1051
Cdd:cd09540      1 PLTYDSSPEEVKAWLQAKGF 20

Epidermal growth factor receptor kinase substrate (EPS8)-like Phosphotyrosine-binding (PTB) domain; EPS8 is a regulator of Rac signaling. It consists of a PTB and an SH3 domain. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains. This cd is part of the Dab-like subgroup.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2023551189   48 ETSQYHVQHLATFIMDKSEAIATVDDAIRKLVQLSSKEKVWAQEMLLQVNDQSLRLLDVESQvwqrqgsrgregspnrdp 127
Cdd:cd01210      1 DTSQYRVEHLATFTLGREEGVQTVEDALRKLKELDAKGRIWSQEMLLQVNDGWVLLLDIETK------------------ 62

                           90       100       110       120       130       140       150       160
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2023551189  128 dtqlglsagagqdeegkgqagqeglrrarlcpsrgdclaesrsasaprpcrayqlwlcprhtahrpgsrvtptalsvaqv 207
Cdd:cd01210        --------------------------------------------------------------------------------

                          170       180       190       200       210       220       230
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 2023551189  208 qpapvaEELENFPLPTVRHSQTVLNQLRYPSVLLLVCQDSEQSKPDIHFFHCDEVEAELVHEDIESALADCRLGK 282
Cdd:cd01210     63 ------EELESFPLSSIQECTAVLSTCSYNSILLLVVQEPDQPKPEMHLFQCDEVGAELLVEDLQKALSGKRSGR 131

Phosphotyrosine-binding domain; The phosphotyrosine-binding domain (PTB, also phosphotyrosine-interaction or PI domain) in the protein tensin tends to be found at the C-terminus. Tensin is a multi-domain protein that binds to actin filaments and functions as a focal-adhesion molecule (focal adhesions are regions of plasma membrane through which cells attach to the extracellular matrix). Human tensin has actin-binding sites, an SH2 (pfam00017) domain and a region similar to the tumour suppressor PTEN. The PTB domain interacts with the cytoplasmic tails of beta integrin by binding to an NPXY motif.

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 2023551189  514 PAPQEELENFPLPTVRHSQTVLNQLRYPSVLLLVCQDSEQSKPDIHFFHCDEVEAELVHEDIESALADCRLGKKMR 589
Cdd:pfam08416   56 NETKEELESYPLDSISHCQAVLNDGRYNSILALVCQEPGQSKPDVHLFQCDELGAELIAEDIESALSDVRLGKPKK 131

Src Homology 3 domain of Epidermal growth factor receptor kinase substrate 8 and similar proteins; This group is composed of Eps8 and Eps8-like proteins including Eps8-like 1-3, among others. These proteins contain N-terminal Phosphotyrosine-binding (PTB), central SH3, and C-terminal effector domains. Eps8 binds either Abi1 (also called E3b1) or Rab5 GTPase activating protein RN-tre through its SH3 domain. With Abi1 and Sos1, it becomes part of a trimeric complex that is required to activate Rac. Together with RN-tre, it inhibits the internalization of EGFR. The SH3 domains of Eps8 and similar proteins recognize peptides containing a PxxDY motif, instead of the classical PxxP motif. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 2023551189  907 YVRILYDFTARNANELSVLKDEVLEVLEDGHQWWKVRNRSGQAGYVPCNILD 958
Cdd:cd11764      1 YVRVLYDFTARNSKELSVLKGEYLEVLDDSRQWWKVRNSRGQVGYVPHNILE 52

SH3 domain; SH3 (Src homology 3) domains are often indicative of a protein involved in signal transduction related to cytoskeletal organization. First described in the Src cytoplasmic tyrosine kinase. The structure is a partly opened beta barrel.

                           10        20        30        40
                   ....*....|....*....|....*....|....*....|....*
gi 2023551189  911 LYDFTARNANELSVLKDEVLEVLED-GHQWWKVRNRSGQAGYVPC 954
Cdd:pfam00018    3 LYDYTAQEPDELSFKKGDIIIVLEKsEDGWWKGRNKGGKEGLIPS 47

SAM domain of EPS8-like subfamily; SAM (sterile alpha motif) domain of EPS8-like subfamily is a putative protein-protein interaction domain. This subfamily includes epidermal growth factor receptor kinase substrate 8 proteins (EPS8) and epidermal growth factor receptor kinase substrate 8-like (EPSL8) 1, 2, 3 proteins with the SAM domain located in the C-terminal effector region. This region is responsible for intracellular protein localization and is involved in small GTPases (such as Rac and Rab5) activation/inhibition. Proteins belonging to this group participate in coordination and integration of multiple signaling pathways; in particular, they play a role in the control of actin dynamics and in receptor endocytosis. They can form complexes with other proteins; for example, in the actin signaling network they interact with SOS1 and E3b1 (Abl1) proteins as well as with CRIB (via SH3 domains) during the actin filament formation, and in the receptor endocytosis their partner is RN-tre protein.

                           10        20
                   ....*....|....*....|
gi 2023551189 1032 PLTYESGPEEVRAWLEAKAF 1051
Cdd:cd09540      1 PLTYDSSPEEVKAWLQAKGF 20

Src homology 3 domains; Src homology 3 (SH3) domains bind to target proteins through sequences containing proline and hydrophobic amino acids. Pro-containing polypeptides may bind to SH3 domains in 2 different binding orientations.

                            10        20
                    ....*....|....*....|....*..
gi 2023551189  1052 VLEDGHQ-WWKVRNRSGQAGYVPCNIL 1077
Cdd:smart00326   29 VLEKSDDgWWKGRLGRGKEGLFPSNYV 55

Epidermal growth factor receptor kinase substrate (EPS8)-like Phosphotyrosine-binding (PTB) domain; EPS8 is a regulator of Rac signaling. It consists of a PTB and an SH3 domain. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains. This cd is part of the Dab-like subgroup.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2023551189   48 ETSQYHVQHLATFIMDKSEAIATVDDAIRKLVQLSSKEKVWAQEMLLQVNDQSLRLLDVESQvwqrqgsrgregspnrdp 127
Cdd:cd01210      1 DTSQYRVEHLATFTLGREEGVQTVEDALRKLKELDAKGRIWSQEMLLQVNDGWVLLLDIETK------------------ 62

                           90       100       110       120       130       140       150       160
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2023551189  128 dtqlglsagagqdeegkgqagqeglrrarlcpsrgdclaesrsasaprpcrayqlwlcprhtahrpgsrvtptalsvaqv 207
Cdd:cd01210        --------------------------------------------------------------------------------

                          170       180       190       200       210       220       230
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 2023551189  208 qpapvaEELENFPLPTVRHSQTVLNQLRYPSVLLLVCQDSEQSKPDIHFFHCDEVEAELVHEDIESALADCRLGK 282
Cdd:cd01210     63 ------EELESFPLSSIQECTAVLSTCSYNSILLLVVQEPDQPKPEMHLFQCDEVGAELLVEDLQKALSGKRSGR 131

Phosphotyrosine-binding domain; The phosphotyrosine-binding domain (PTB, also phosphotyrosine-interaction or PI domain) in the protein tensin tends to be found at the C-terminus. Tensin is a multi-domain protein that binds to actin filaments and functions as a focal-adhesion molecule (focal adhesions are regions of plasma membrane through which cells attach to the extracellular matrix). Human tensin has actin-binding sites, an SH2 (pfam00017) domain and a region similar to the tumour suppressor PTEN. The PTB domain interacts with the cytoplasmic tails of beta integrin by binding to an NPXY motif.

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 2023551189  514 PAPQEELENFPLPTVRHSQTVLNQLRYPSVLLLVCQDSEQSKPDIHFFHCDEVEAELVHEDIESALADCRLGKKMR 589
Cdd:pfam08416   56 NETKEELESYPLDSISHCQAVLNDGRYNSILALVCQEPGQSKPDVHLFQCDELGAELIAEDIESALSDVRLGKPKK 131

Src Homology 3 domain of Epidermal growth factor receptor kinase substrate 8 and similar proteins; This group is composed of Eps8 and Eps8-like proteins including Eps8-like 1-3, among others. These proteins contain N-terminal Phosphotyrosine-binding (PTB), central SH3, and C-terminal effector domains. Eps8 binds either Abi1 (also called E3b1) or Rab5 GTPase activating protein RN-tre through its SH3 domain. With Abi1 and Sos1, it becomes part of a trimeric complex that is required to activate Rac. Together with RN-tre, it inhibits the internalization of EGFR. The SH3 domains of Eps8 and similar proteins recognize peptides containing a PxxDY motif, instead of the classical PxxP motif. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 2023551189  907 YVRILYDFTARNANELSVLKDEVLEVLEDGHQWWKVRNRSGQAGYVPCNILD 958
Cdd:cd11764      1 YVRVLYDFTARNSKELSVLKGEYLEVLDDSRQWWKVRNSRGQVGYVPHNILE 52

Src Homology 3 domain superfamily; Src Homology 3 (SH3) domains are protein interaction domains that bind proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. Thus, they are referred to as proline-recognition domains (PRDs). SH3 domains are less selective and show more diverse specificity compared to other PRDs. They have been shown to bind peptide sequences that lack the PxxP motif; examples include the PxxDY motif of Eps8 and the RKxxYxxY sequence in SKAP55. SH3 domain containing proteins play versatile and diverse roles in the cell, including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies, among others. Many members of this superfamily are adaptor proteins that associate with a number of protein partners, facilitating complex formation and signal transduction.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|
gi 2023551189  907 YVRILYDFTARNANELSVLKDEVLEVLE-DGHQWWKVRNRSGQAGYVPCN 955
Cdd:cd00174      1 YARALYDYEAQDDDELSFKKGDIITVLEkDDDGWWEGELNGGREGLFPAN 50

Src Homology 3 domain of Tec-like Protein Tyrosine Kinases; The Tec (Tyrosine kinase expressed in hepatocellular carcinoma) subfamily is composed of Tec, Btk, Bmx (Etk), Itk (Tsk, Emt), Rlk (Txk), and similar proteins. They are cytoplasmic (or nonreceptor) tyr kinases containing Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. Most Tec subfamily members (except Rlk) also contain an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation. In addition, some members contain the Tec homology (TH) domain, which contains proline-rich and zinc-binding regions. Tec kinases are expressed mainly by haematopoietic cells, although Tec and Bmx are also found in endothelial cells. B-cells express Btk and Tec, while T-cells express Itk, Txk, and Tec. Collectively, Tec kinases are expressed in a variety of myeloid cells such as mast cells, platelets, macrophages, and dendritic cells. Each Tec kinase shows a distinct cell-type pattern of expression. The function of Tec kinases in lymphoid cells have been studied extensively. They play important roles in the development, differentiation, maturation, regulation, survival, and function of B-cells and T-cells. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|...
gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVLED-GHQWWKVRNRSGQAGYVPCNILDE 959
Cdd:cd11768      2 VVALYDFQPIEPGDLPLEKGEEYVVLDDsNEHWWRARDKNGNEGYIPSNYVTE 54

First Src Homology 3 domain of FCH and double SH3 domains proteins; This group is composed of FCH and double SH3 domains protein 1 (FCHSD1) and FCHSD2. These proteins have a common domain structure consisting of an N-terminal F-BAR (FES-CIP4 Homology and Bin/Amphiphysin/Rvs), two SH3, and C-terminal proline-rich domains. They have only been characterized in silico and their functions remain unknown. This group also includes the insect protein, nervous wreck, which acts as a regulator of synaptic growth signaling. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|.
gi 2023551189  910 ILYDFTARNANELSVLKDEVLEVLEDG--HQWWKVRNRSGQAGYVPCNILD 958
Cdd:cd11761      6 VLYSYEAQRPDELTITEGEELEVIEDGdgDGWVKARNKSGEVGYVPENYLQ 56

Src homology 3 domain of Src kinase-like Protein Tyrosine Kinases; Src subfamily members include Src, Lck, Hck, Blk, Lyn, Fgr, Fyn, Yrk, Yes, and Brk. Src (or c-Src) proteins are cytoplasmic (or non-receptor) PTKs which are anchored to the plasma membrane. They contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). However, Brk lacks the N-terminal myristoylation sites. Src proteins are involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. They were identified as the first proto-oncogene products, and they regulate cell adhesion, invasion, and motility in cancer cells, and tumor vasculature, contributing to cancer progression and metastasis. Src kinases are overexpressed in a variety of human cancers, making them attractive targets for therapy. They are also implicated in acute inflammatory responses and osteoclast function. Src, Fyn, Yes, and Yrk are widely expressed, while Blk, Lck, Hck, Fgr, Lyn, and Brk show a limited expression pattern. This subfamily also includes Drosophila Src42A, Src oncogene at 42A (also known as Dsrc41) which accumulates at sites of cell-cell or cell-matrix adhesion, and participates in Drosphila development and wound healing. It has been shown to promote tube elongation in the tracheal system, is essential for proper cell-cell matching during dorsal closure, and regulates cell-cell contacts in developing Drosophila eyes. The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40
                   ....*....|....*....|....*....|....*....|....*..
gi 2023551189  911 LYDFTARNANELSVLKDEVLEVLEDGH-QWWKVRN-RSGQAGYVPCN 955
Cdd:cd11845      5 LYDYEARTDDDLSFKKGDRLQILDDSDgDWWLARHlSTGKEGYIPSN 51

Src Homology 3 domain of Bruton's tyrosine kinase; BTK is a cytoplasmic (or nonreceptor) tyr kinase containing Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. It also contains an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation, and the Tec homology (TH) domain with proline-rich and zinc-binding regions. Btk is expressed in B-cells, and a variety of myeloid cells including mast cells, platelets, neutrophils, and dendrictic cells. It interacts with a variety of partners, from cytosolic proteins to nuclear transcription factors, suggesting a diversity of functions. Stimulation of a diverse array of cell surface receptors, including antigen engagement of the B-cell receptor (BCR), leads to PH-mediated membrane translocation of Btk and subsequent phosphorylation by Src kinase and activation. Btk plays an important role in the life cycle of B-cells including their development, differentiation, proliferation, survival, and apoptosis. Mutations in Btk cause the primary immunodeficiency disease, X-linked agammaglobulinaemia (XLA) in humans. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|....*
gi 2023551189  906 KYVRILYDFTARNANELSVLKDEVLEVLEDG-HQWWKVRNRSGQAGYVPCNILDE 959
Cdd:cd11906      1 KKVVALYDYTPMNAQDLQLRKGEEYVILEESnLPWWRARDKNGREGYIPSNYVTE 55

Src Homology 3 domain of fungal peroxisomal membrane protein Pex13p; Pex13p, located in the peroxisomal membrane, contains two transmembrane regions and a C-terminal SH3 domain. It binds to the peroxisomal targeting type I (PTS1) receptor Pex5p and the docking factor Pex14p through its SH3 domain. It is essential for both PTS1 and PTS2 protein import pathways into the peroxisomal matrix. Pex13p binds Pex14p, which contains a PxxP motif, in a classical fashion to the proline-rich ligand binding site of its SH3 domain. It binds the WxxxF/Y motif of Pex5p in a novel site that does not compete with Pex14p binding. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|....*.
gi 2023551189  907 YVRILYDFTARN-ANELSVLKDEVLEVL------EDGHQWWKVRNRSGQAGYVPCN 955
Cdd:cd11771      1 FCRALYDFTPENpEMELSLKKGDIVAVLsktdplGRDSEWWKGRTRDGRIGWFPSN 56

Src homology 3 domain of Proline-Serine-Threonine Phosphatase-Interacting Protein 1; PSTPIP1, also called CD2 Binding Protein 1 (CD2BP1), is mainly expressed in hematopoietic cells. It is a binding partner of the cell surface receptor CD2 and PTP-PEST, a tyrosine phosphatase which functions in cell motility and Rac1 regulation. It also plays a role in the activation of the Wiskott-Aldrich syndrome protein (WASP), which couples actin rearrangement and T cell activation. Mutations in the gene encoding PSTPIP1 cause the autoinflammatory disorder known as PAPA (pyogenic sterile arthritis, pyoderma gangrenosum, and acne) syndrome. PSTPIP1 contains an N-terminal F-BAR domain, PEST motifs, and a C-terminal SH3 domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|
gi 2023551189  909 RILYDFTARNANELSVLKDEVLEVLEDGHQ-WWKVRnRSGQAGYVPCNIL 957
Cdd:cd11824      3 SVLYDYTAQEDDELSISKGDVVAVIEKGEDgWWTVE-RNGQKGLVPGTYL 51

First Src Homology 3 domain of Nck2 adaptor protein; Nck2 (also called Nckbeta or Growth factor receptor-bound protein 4, Grb4) plays a crucial role in connecting signaling pathways of tyrosine kinase receptors and important effectors in actin dynamics and cytoskeletal remodeling. It binds neuronal signaling proteins such as ephrinB and Disabled-1 (Dab-1) exclusively. Nck adaptor proteins regulate actin cytoskeleton dynamics by linking proline-rich effector molecules to protein tyrosine kinases and phosphorylated signaling intermediates. They contain three SH3 domains and a C-terminal SH2 domain. They function downstream of the PDGFbeta receptor and are involved in Rho GTPase signaling and actin dynamics. Vertebrates contain two Nck adaptor proteins: Nck1 (also called Nckalpha) and Nck2, which show partly overlapping functions but also bind distinct targets. The first SH3 domain of Nck2 binds the PxxDY sequence in the CD3e cytoplasmic tail; this binding inhibits phosphorylation by Src kinases, resulting in the downregulation of TCR surface expression. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity, preferentially a PxxP motif. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40
                   ....*....|....*....|....*....|....*....|....*..
gi 2023551189  912 YDFTARNANELSVLKDEVLEVLEDGHQWWKVRNRSGQAGYVPCNILD 958
Cdd:cd11899     10 WDYTAQQDQELDIKKNERLWLLDDSKTWWRVRNAANRTGYVPSNYVE 56

Src homology 3 domain of High osmolarity signaling protein Sho1p; Sho1p (or Sho1), also called SSU81 (Suppressor of SUA8-1 mutation), is a yeast membrane protein that regulates adaptation to high salt conditions by activating the HOG (high-osmolarity glycerol) pathway. High salt concentrations lead to the localization to the membrane of the MAPKK Pbs2, which is then activated by the MAPKK Ste11 and in turn, activates the MAPK Hog1. Pbs2 is localized to the membrane though the interaction of its PxxP motif with the SH3 domain of Sho1p. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 2023551189  908 VRILYDFTA--RNANELSVLKDEVLEVLEDGHQWWKVRNRSGQAGYVPCNIL 957
Cdd:cd11855      2 ARALYPYDAspDDPNELSFEKGEILEVSDTSGKWWQARKSNGETGICPSNYL 53

Third Src Homology 3 domain of the fungal endocytic adaptor protein Sla1p; Sla1p facilitates endocytosis by playing a role as an adaptor protein in coupling components of the actin cytoskeleton to the endocytic machinery. It interacts with Abp1p, Las17p and Pan1p, which are activator proteins of actin-related protein 2/3 (Arp2/3). Sla1p contains multiple domains including three SH3 domains, a SAM (sterile alpha motif) domain, and a Sla1 homology domain 1 (SHD1), which binds to the NPFXD motif that is found in many integral membrane proteins such as the Golgi-localized Arf-binding protein Lsb5p and the P4-ATPases, Drs2p and Dnf1p. The third SH3 domain of Sla1p can bind ubiquitin while retaining the ability to bind proline-rich ligands; monoubiquitination of target proteins signals internalization and sorting through the endocytic pathway. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  906 KYVRILYDFTARNANELSVLKDEVLEVLED--GHQWWKVRNRS-GQAGYVPCNILD 958
Cdd:cd11775      1 KRGKVLYDFDAQSDDELTVKEGDVVYILDDkkSKDWWMVENVStGKEGVVPASYIE 56

Src homology 3 domain of Type I fungal Myosins; Type I myosins (myosin-I) are actin-dependent motors in endocytic actin structures and actin patches. They play roles in membrane traffic in endocytic and secretory pathways, cell motility, and mechanosensing. Saccharomyces cerevisiae has two myosins-I, Myo3 and Myo5, which are involved in endocytosis and the polarization of the actin cytoskeleton. Myosin-I contains an N-terminal actin-activated ATPase, a phospholipid-binding TH1 (tail homology 1) domain, and a C-terminal extension which includes an F-actin-binding TH2 domain, an SH3 domain, and an acidic peptide that participates in activating the Arp2/3complex. The SH3 domain of myosin-I is required for myosin-I-induced actin polymerization. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  909 RILYDFTARNANELSVLKDEVLEVLE-DGHQWWKVRNRSGQA-GYVPCNILDE 959
Cdd:cd11858      3 KALYDFAGSVANELSLKKDDIVYIVQkEDNGWWLAKKLDESKeGWVPAAYLEE 55

Variant SH3 domain;

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gi 2023551189  911 LYDFTARNANELSVLKDEVLEVLEDGHQ-WWKVRNRsGQAGYVPCNILD 958
Cdd:pfam14604    2 LYPYEPKDDDELSLQRGDVITVIEESEDgWWEGINT-GRTGLVPANYVE 49

Third Src Homology 3 domain of Nck2 adaptor protein; Nck2 (also called Nckbeta or Growth factor receptor-bound protein 4, Grb4) plays a crucial role in connecting signaling pathways of tyrosine kinase receptors and important effectors in actin dynamics and cytoskeletal remodeling. It binds neuronal signaling proteins such as ephrinB and Disabled-1 (Dab-1) exclusively. Nck adaptor proteins regulate actin cytoskeleton dynamics by linking proline-rich effector molecules to protein tyrosine kinases and phosphorylated signaling intermediates. They contain three SH3 domains and a C-terminal SH2 domain. They function downstream of the PDGFbeta receptor and are involved in Rho GTPase signaling and actin dynamics. Vertebrates contain two Nck adaptor proteins: Nck1 (also called Nckalpha) and Nck2, which show partly overlapping functions but also bind distinct targets. The third SH3 domain of Nck appears to prefer ligands with a PxAPxR motif. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity, preferentially a PxxP motif. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVLE---DGHQWWKVRNRSGQAGYVPCN 955
Cdd:cd11903      3 VQTLYPFSSVTEEELNFEKGETMEVIEkpeNDPEWWKCKNSRGQVGLVPKN 53

First Src Homology 3 domain of Nck1 adaptor protein; Nck1 (also called Nckalpha) plays a crucial role in connecting signaling pathways of tyrosine kinase receptors and important effectors in actin dynamics and cytoskeletal remodeling. It binds and activates RasGAP, resulting in the downregulation of Ras. It is also involved in the signaling of endothilin-mediated inhibition of cell migration. Nck adaptor proteins regulate actin cytoskeleton dynamics by linking proline-rich effector molecules to protein tyrosine kinases and phosphorylated signaling intermediates. They contain three SH3 domains and a C-terminal SH2 domain. They function downstream of the PDGFbeta receptor and are involved in Rho GTPase signaling and actin dynamics. Vertebrates contain two Nck adaptor proteins: Nck1 (also called Nckalpha) and Nck2, which show partly overlapping functions but also bind distinct targets. The first SH3 domain of Nck1 binds the PxxDY sequence in the CD3e cytoplasmic tail; this binding inhibits phosphorylation by Src kinases, resulting in the downregulation of TCR surface expression. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity, preferentially a PxxP motif. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  912 YDFTARNANELSVLKDEVLEVLEDGHQWWKVRNRSGQAGYVPCNILD 958
Cdd:cd11900      9 FDYVAQQDQELDIKKNERLWLLDDSKSWWRVRNAMNKTGFVPSNYVE 55

Src Homology 3 domain of Interleukin-2-inducible T-cell Kinase; ITK (also known as Tsk or Emt) is a cytoplasmic (or nonreceptor) tyr kinase containing Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. It also contains an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation, and the Tec homology (TH) domain, which contains proline-rich and zinc-binding regions. ITK is expressed in T-cells and mast cells, and is important in their development and differentiation. Of the three Tec kinases expressed in T-cells, ITK plays the predominant role in T-cell receptor (TCR) signaling. It is activated by phosphorylation upon TCR crosslinking and is involved in the pathway resulting in phospholipase C-gamma1 activation and actin polymerization. It also plays a role in the downstream signaling of the T-cell costimulatory receptor CD28, the T-cell surface receptor CD2, and the chemokine receptor CXCR4. In addition, ITK is crucial for the development of T-helper(Th)2 effector responses. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVLEDGH-QWWKVRNRSGQAGYVPCNILDE 959
Cdd:cd11908      3 VIALYDYQTNDPQELALRYNEEYHLLDSSEiHWWRVQDKNGHEGYVPSSYLVE 55

Fifth Src homology 3 domain (or SH3E) of Intersectin; Intersectins (ITSNs) are adaptor proteins that function in exo- and endocytosis, actin cytoskeletal reorganization, and signal transduction. They are essential for initiating clathrin-coated pit formation. They bind to many proteins through their multidomain structure and facilitate the assembly of multimeric complexes. Vertebrates contain two ITSN proteins, ITSN1 and ITSN2, which exist in alternatively spliced short and long isoforms. The short isoforms contain two Eps15 homology domains (EH1 and EH2), a coiled-coil region and five SH3 domains (SH3A-E), while the long isoforms, in addition, contain RhoGEF (also called Dbl-homologous or DH), Pleckstrin homology (PH) and C2 domains. ITSN1 and ITSN2 are both widely expressed, with variations depending on tissue type and stage of development. The fifth SH3 domain (or SH3E) of ITSN1 has been shown to bind many protein partners including SGIP1, Sos1, dynamin1/2, CIN85, c-Cbl, SHIP2, N-WASP, and synaptojanin-1, among others. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVL-EDGHQWWKvRNRSGQAGYVPCN 955
Cdd:cd11840      2 VIALFPYTAQNEDELSFQKGDIINVLsKDDPDWWR-GELNGQTGLFPSN 49

Src Homology 3 domain of metazoan osteoclast stimulating factor 1; OSTF1, also named OSF or SH3P2, is a signaling protein containing SH3 and ankyrin-repeat domains. It acts through a Src-related pathway to enhance the formation of osteoclasts and bone resorption. It also acts as a negative regulator of cell motility. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVLE-DGHQWWKVRNRsGQAGYVPCNILDE 959
Cdd:cd11772      2 FRALYDYEAQHPDELSFEEGDLLYISDkSDPNWWKATCG-GKTGLIPSNYVEE 53

Src Homology 3 domain of TXK, also called Resting lymphocyte kinase (Rlk); TXK is a cytoplasmic (or nonreceptor) tyr kinase containing Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. It also contains an N-terminal cysteine-rich region. Rlk is expressed in T-cells and mast cell lines, and is a key component of T-cell receptor (TCR) signaling. It is important in TCR-stimulated proliferation, IL-2 production and phospholipase C-gamma1 activation. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVLE--DGHqWWKVRNRSGQAGYVPCNILDE 959
Cdd:cd11907      3 VKALYDFLPREPSNLALKRAEEYLILEqyDPH-WWKARDRYGNEGLIPSNYVTE 55

Src homology 3 domain of Signal Transducing Adaptor Molecules; STAMs were discovered as proteins that are highly phosphorylated following cytokine and growth factor stimulation. They function in cytokine signaling and surface receptor degradation, as well as regulate Golgi morphology. They associate with many proteins including Jak2 and Jak3 tyrosine kinases, Hrs, AMSH, and UBPY. STAM adaptor proteins contain VHS (Vps27, Hrs, STAM homology), ubiquitin interacting (UIM), and SH3 domains. There are two vertebrate STAMs, STAM1 and STAM2, which may be functionally redundant; vertebrate STAMs contain ITAM motifs. They are part of the endosomal sorting complex required for transport (ESCRT-0). STAM2 deficiency in mice did not cause any obvious abnormality, while STAM1 deficiency resulted in growth retardation. Loss of both STAM1 and STAM2 in mice proved lethal, indicating that STAMs are important for embryonic development. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVLEDGH-QWWKVRNRSGQaGYVPCN 955
Cdd:cd11820      3 VRALYDFEAAEDNELTFKAGEIITVLDDSDpNWWKGSNHRGE-GLFPAN 50

Src homology 3 domain of Srms Protein Tyrosine Kinase; Src-related kinase lacking C-terminal regulatory tyrosine and N-terminal myristoylation sites (Srms) is a cytoplasmic (or non-receptor) PTK with limited homology to Src kinases. Src kinases in general contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr; they are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). However, Srms lacks the N-terminal myristoylation sites. Src proteins are involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  911 LYDFTARNANELSVLKDEVLEVLEDGHQWWKVRNRSGQ--AGYVPCN 955
Cdd:cd11846      5 LYDFTARSTHELSVEQGDKLCVIEEEGDYIFARKLTGNpeSGLVPAS 51

Src homology 3 domain of Signal Transducing Adaptor Molecule 2; STAM2, also called EAST (Epidermal growth factor receptor-associated protein with SH3 and TAM domain) or Hbp (Hrs binding protein), is part of the endosomal sorting complex required for transport (ESCRT-0). It plays a role in sorting mono-ubiquinated endosomal cargo for trafficking to the lysosome for degradation. It is also involved in the regulation of exocytosis. STAMs were discovered as proteins that are highly phosphorylated following cytokine and growth factor stimulation. They function in cytokine signaling and surface receptor degradation, as well as regulate Golgi morphology. They associate with many proteins including Jak2 and Jak3 tyrosine kinases, Hrs, AMSH, and UBPY. STAM adaptor proteins contain VHS (Vps27, Hrs, STAM homology), ubiquitin interacting (UIM), and SH3 domains. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVLEDGH-QWWKVRNRSGqAGYVPCNIL 957
Cdd:cd11963      4 VRALYDFEAVEDNELTFKHGEIIIVLDDSDaNWWKGENHRG-VGLFPSNFV 53

Src homology 3 domain of Endophilin-B; Endophilins play roles in synaptic vesicle formation, virus budding, mitochondrial morphology maintenance, receptor-mediated endocytosis inhibition, and endosomal sorting. They are classified into two types, A and B. Vertebrates contain two endophilin-B isoforms. Endophilin-B proteins are cytoplasmic proteins expressed mainly in the heart, placenta, and skeletal muscle. Endophilins contain an N-terminal N-BAR domain (BAR domain with an additional N-terminal amphipathic helix), followed by a variable region containing proline clusters, and a C-terminal SH3 domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  909 RILYDFTARNANELSVLKDEVLEVLE--DGHQWWKVRNRSGQAGYVP 953
Cdd:cd11802      3 RVLYDYDAEDSTELSLLADEVITVYElpGMDEDYMMGERGSQRGKVP 49

Second C-terminal Src homology 3 domain of Dynamin Binding Protein, also called Tuba, and similar domains; DNMBP or Tuba is a cdc42-specific guanine nucleotide exchange factor (GEF) that contains four N-terminal SH3 domains, a central RhoGEF [or Dbl homology (DH)] domain followed by a Bin/Amphiphysin/Rvs (BAR) domain, and two C-terminal SH3 domains. It provides a functional link between dynamin, Rho GTPase signaling, and actin dynamics. It plays an important role in regulating cell junction configuration. The C-terminal SH3 domains of DNMBP bind to N-WASP and Ena/VASP proteins, which are key regulatory proteins of the actin cytoskeleton. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  911 LYDFTARNANELSVLKDEVLEVLE----DGHQWWKVRNRSGQAGYVPCNIL 957
Cdd:cd12141      5 VYTFKARSPNELSVSANQRVRILEfsdlTGNKEWWLAEANGQKGYVPSNYI 55

Src homology 3 domain of Cortactin and related proteins; This subfamily includes cortactin, Abp1 (actin-binding protein 1), hematopoietic lineage cell-specific protein 1 (HS1), and similar proteins. These proteins are involved in regulating actin dynamics through direct or indirect interaction with the Arp2/3 complex, which is required to initiate actin polymerization. They all contain at least one C-terminal SH3 domain. Cortactin and HS1 bind Arp2/3 and actin through an N-terminal region that contains an acidic domain and several copies of a repeat domain found in cortactin and HS1. Abp1 binds actin via an N-terminal actin-depolymerizing factor (ADF) homology domain. Yeast Abp1 binds Arp2/3 directly through two acidic domains. Mammalian Abp1 does not directly interact with Arp2/3; instead, it regulates actin dynamics indirectly by interacting with dynamin and WASP family proteins. The C-terminal region of these proteins acts as an adaptor or scaffold that can connect membrane trafficking and signaling proteins that bind the SH3 domain within the actin network. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  909 RILYDFTARNANELSVLKDEVLEVLE---DGhqWWKVRNRSGQAGYVPCN 955
Cdd:cd11819      3 KALYDYQAAEDNEISFVEGDIITQIEqidEG--WWLGVNAKGQKGLFPAN 50

Src Homology 3 domain of Tec-like Protein Tyrosine Kinases; The Tec (Tyrosine kinase expressed in hepatocellular carcinoma) subfamily is composed of Tec, Btk, Bmx (Etk), Itk (Tsk, Emt), Rlk (Txk), and similar proteins. They are cytoplasmic (or nonreceptor) tyr kinases containing Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. Most Tec subfamily members (except Rlk) also contain an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation. In addition, some members contain the Tec homology (TH) domain, which contains proline-rich and zinc-binding regions. Tec kinases are expressed mainly by haematopoietic cells, although Tec and Bmx are also found in endothelial cells. B-cells express Btk and Tec, while T-cells express Itk, Txk, and Tec. Collectively, Tec kinases are expressed in a variety of myeloid cells such as mast cells, platelets, macrophages, and dendritic cells. Each Tec kinase shows a distinct cell-type pattern of expression. The function of Tec kinases in lymphoid cells have been studied extensively. They play important roles in the development, differentiation, maturation, regulation, survival, and function of B-cells and T-cells. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189 1051 FVLED-GHQWWKVRNRSGQAGYVPCNILDE 1079
Cdd:cd11768     25 VVLDDsNEHWWRARDKNGNEGYIPSNYVTE 54

N-terminal (or first) Src Homology 3 domain of the p67phox subunit of NADPH oxidase; p67phox, also called Neutrophil cytosol factor 2 (NCF-2), is a cytosolic subunit of the phagocytic NADPH oxidase complex (also called Nox2 or gp91phox) which plays a crucial role in the cellular response to bacterial infection. NADPH oxidase catalyzes the transfer of electrons from NADPH to oxygen during phagocytosis forming superoxide and reactive oxygen species. p67phox plays a regulatory role and contains N-terminal TPR, first SH3 (or N-terminal or central SH3), PB1, and C-terminal SH3 domains. It binds, via its C-terminal SH3 domain, to a proline-rich region of p47phox and upon activation, this complex assembles with flavocytochrome b558, the Nox2-p22phox heterodimer. Concurrently, RacGTP translocates to the membrane and interacts with the TPR domain of p67phox, which leads to the activation of NADPH oxidase. The PB1 domain of p67phox binds to its partner PB1 domain in p40phox, and this facilitates the assembly of p47phox-p67phox at the membrane. The N-terminal SH3 domain increases the affinity of p67phox for the oxidase complex. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  909 RILYDFTARNANELSVLKDEVLEVLEDGHQWWKVRNRSGQAGYVPCNILD 958
Cdd:cd11871      3 RVLYEFVPETKEELQVLPGNIVFVLKKGTDNWATVVFNGKKGLVPCNFLE 52

Src homology 3 domain of Endophilin-B1; Endophilin-B1, also called Bax-interacting factor 1 (Bif-1) or SH3GLB1 (SH3-domain GRB2-like endophilin B1), is localized mainly to the Golgi apparatus. It is involved in the regulation of many biological events including autophagy, tumorigenesis, nerve growth factor (NGF) trafficking, neurite outgrowth, mitochondrial outer membrane dynamics, and cell death. Endophilins play roles in synaptic vesicle formation, virus budding, mitochondrial morphology maintenance, receptor-mediated endocytosis inhibition, and endosomal sorting. They contain an N-terminal N-BAR domain (BAR domain with an additional N-terminal amphipathic helix), followed by a variable region containing proline clusters, and a C-terminal SH3 domain. Endophilin-B1 forms homo- and heterodimers (with endophilin-B2) through its BAR domain. It interacts with amphiphysin 1 and dynamin 1 through its SH3 domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  905 TKYVRILYDFTARNANELSVLKDEVLEVLE----DGHqwWKVRNRSGQAGYVPCNILD 958
Cdd:cd11945      3 SRKARVLYDYDAANSTELSLLADEVITVYSvpgmDSD--WLMGERGNQKGKVPITYLE 58

Phosphotyrosine-binding domain, phosphotyrosine-interaction (PI) domain; PTB/PI domain structure similar to those of pleckstrin homology (PH) and IRS-1-like PTB domains.

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gi 2023551189    51 QYHVQHLATFIMDKSEAIATVDDAIRKLVQLSSKEKVWAQEMLLQVNDQSLRLLDVESQ 109
Cdd:smart00462    5 SFRVKYLGSVEVPEARGLQVVQEAIRKLRAAQGSEKKEPQKVILSISSRGVKLIDEDTK 63

N-terminal Src homology 3 domain of Growth factor receptor-bound protein 2 (GRB2) and related proteins; This family includes the adaptor protein GRB2 and related proteins including Drosophila melanogaster Downstream of receptor kinase (DRK), Caenorhabditis elegans Sex muscle abnormal protein 5 (Sem-5), GRB2-related adaptor protein (GRAP), GRAP2, and similar proteins. Family members contain an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. GRB2/Sem-5/DRK is a critical signaling molecule that regulates the Ras pathway by linking tyrosine kinases to the Ras guanine nucleotide releasing protein Sos (son of sevenless), which converts Ras to the active GTP-bound state. GRAP2 plays an important role in T cell receptor (TCR) signaling by promoting the formation of the SLP-76:LAT complex, which couples the TCR to the Ras pathway. GRAP acts as a negative regulator of T cell receptor (TCR)-induced lymphocyte proliferation by downregulating the signaling to the Ras/ERK pathway. The N-terminal SH3 domain of GRB2 binds to Sos and Sos-derived proline-rich peptides. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  911 LYDFTARNANELSVLKDEVLEVL--EDGHQWWKVRNRsGQAGYVPCN 955
Cdd:cd11804      5 KHDFKATAEDELSFKKGSILKVLnmEDDPNWYKAELD-GKEGLIPKN 50

Src homology 3 domain of Protein kinase C and Casein kinase Substrate in Neurons (PACSIN) proteins; PACSINs, also called Synaptic dynamin-associated proteins (Syndapins), act as regulators of cytoskeletal and membrane dynamics. They bind both dynamin and Wiskott-Aldrich syndrome protein (WASP), and may provide direct links between the actin cytoskeletal machinery through WASP and dynamin-dependent endocytosis. Vetebrates harbor three isoforms with distinct expression patterns and specific functions. PACSINs contain an N-terminal F-BAR domain and a C-terminal SH3 domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVL--EDGHQWWKVRNRsGQAGYVPCN 955
Cdd:cd11843      2 VRALYDYEGQESDELSFKAGDILTKLeeEDEQGWCKGRLD-GRVGLYPAN 50

Src homology 3 domain of Signal Transducing Adaptor Molecule 1; STAM1 is part of the endosomal sorting complex required for transport (ESCRT-0) and is involved in sorting ubiquitinated cargo proteins from the endosome. It may also be involved in the regulation of IL2 and GM-CSF mediated signaling, and has been implicated in neural cell survival. STAMs were discovered as proteins that are highly phosphorylated following cytokine and growth factor stimulation. They function in cytokine signaling and surface receptor degradation, as well as regulate Golgi morphology. They associate with many proteins including Jak2 and Jak3 tyrosine kinases, Hrs, AMSH, and UBPY. STAM adaptor proteins contain VHS (Vps27, Hrs, STAM homology), ubiquitin interacting (UIM), and SH3 domains. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  906 KYVRILYDFTARNANELSVLKDEVLEVLEDGH-QWWKVRNRSGqAGYVPCNIL 957
Cdd:cd11964      1 RKVRAIYDFEAAEDNELTFKAGDIITILDDSDpNWWKGETPQG-TGLFPSNFV 52

Src homology 3 domain of Lyn Protein Tyrosine Kinase; Lyn is a member of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) PTKs. Lyn is expressed in B lymphocytes and myeloid cells. It exhibits both positive and negative regulatory roles in B cell receptor (BCR) signaling. Lyn, as well as Fyn and Blk, promotes B cell activation by phosphorylating ITAMs (immunoreceptor tyr activation motifs) in CD19 and in Ig components of BCR. It negatively regulates signaling by its unique ability to phosphorylate ITIMs (immunoreceptor tyr inhibition motifs) in cell surface receptors like CD22 and CD5. Lyn also plays an important role in G-CSF receptor signaling by phosphorylating a variety of adaptor molecules. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  911 LYDFTARNANELSVLKDEVLEVLEDGHQWWKVRNRSGQA-GYVPCN 955
Cdd:cd12004      5 LYPYDGIHEDDLSFKKGEKLKVIEEHGEWWKARSLTTKKeGFIPSN 50

Src homology 3 domain of Lck Protein Tyrosine Kinase; Lck is a member of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) PTKs. Lck is expressed in T-cells and natural killer cells. It plays a critical role in T-cell maturation, activation, and T-cell receptor (TCR) signaling. Lck phosphorylates ITAM (immunoreceptor tyr activation motif) sequences on several subunits of TCRs, leading to the activation of different second messenger cascades. Phosphorylated ITAMs serve as binding sites for other signaling factor such as Syk and ZAP-70, leading to their activation and propagation of downstream events. In addition, Lck regulates drug-induced apoptosis by interfering with the mitochondrial death pathway. The apototic role of Lck is independent of its primary function in T-cell signaling. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2023551189  908 VRILYDFTARNANELSVLKDEVLEVLEDGHQWWKVRN-RSGQAGYVPCN 955
Cdd:cd12005      2 VVALYSYEPSHDGDLGFEKGEKLRILEQSGEWWKAQSlTTGQEGFIPFN 50