Src Homology 3 domain of Disks large homolog proteins
The DLG-like proteins are scaffolding proteins that cluster at synapses and are also called PSD (postsynaptic density)-95 proteins or SAPs (synapse-associated proteins). They play important roles in synaptic development and plasticity, cell polarity, migration and proliferation. They are members of the MAGUK (membrane-associated guanylate kinase) protein family, which is characterized by the presence of a core of three domains: PDZ, SH3, and guanylate kinase (GuK). The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. DLG-like proteins contain three PDZ domains and varying N-terminal regions. All DLG proteins exist as alternatively-spliced isoforms. Vertebrates contain four DLG proteins from different genes, called DLG1-4. DLG4 and DLG2 are found predominantly at postsynaptic sites and they mediate surface ion channel and receptor clustering. DLG3 is found axons and some presynaptic terminals. DLG1 interacts with AMPA-type glutamate receptors and is critical in their maturation and delivery to synapses. The SH3 domain of DLG4 binds and clusters the kainate subgroup of glutamate receptors via two proline-rich sequences in their C-terminal tail. It also binds AKAP79/150 (A-kinase anchoring protein). 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.
Comment:The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",