Conserved Protein Domain Family

cd07019: S49_SppA_1 
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Signal peptide peptidase A (SppA), a serine protease, has catalytic Ser-Lys dyad
Signal peptide peptidase A (SppA; Peptidase S49; Protease IV): SppAs in this subfamily are found in all three domains of life and are involved in the cleavage of signal peptides after their removal from the precursor proteins by signal peptidases. Site-directed mutagenesis and sequence analysis have shown these bacterial, archaeal and thylakoid SppAs to be serine proteases. The predicted active site serine for members in this family occurs in a transmembrane domain. Mutagenesis studies also suggest that the catalytic center comprises a Ser-Lys dyad (both residues absolutely conserved within bacteria, chloroplast and mitochondrial signal peptidase family members) and not the usual Ser-His-Asp catalytic triad found in the majority of serine proteases. In addition to the carboxyl-terminal protease domain that is conserved in all the S49 family members, the E. coli SppA contains an amino-terminal domain, similar to Arabidopsis thaliana SppA1 peptidase. Others, including sohB peptidase, protein C and archaeal signal peptide peptidase, do not contain the amino-terminal domain. Interestingly, the single membrane spanning E. coli SppA carries out catalysis using a Ser-Lys dyad with the serine located in the conserved carboxy-terminal protease domain and the lysine in the non-conserved amino-terminal domain.
PSSM-Id: 132930
Aligned: 3 rows
Threshold Bit Score: 258.033
Created: 25-Nov-2008
Updated: 2-Oct-2020
Aligned Rows:
Conserved site include 1 residue -Click on image for an interactive view with Cn3D
Feature 1:active site residues [active site]
  • Comment:The N- and C-terminal halves of SppA in E. coli are tandem repeats and the Ser/Lys dyad is arranged such that the nucleophile Ser is located in the C-terminal half whereas the general base Lys is located in the N-terminal half.
  • Structure:3BEZ: Escherichia coli Signal peptide peptidase A (SppA)
    View structure with Cn3D

Sequence Alignment
Format: Row Display: Color Bits: Type Selection:
Feature 1                                                                                     
3BF0_A    302 SIGVVFANGaimdgee----tqgnvgGDTTAAQIRDARLdpkvKAIVLRVNSPggsvTASEVIRAELAAARaa-gKPVVV 376 Escherichia coli
3BEZ_A    302 SIGVVFANGaixdgee----tqgnvgGDTTAAQIRDARLdpkvKAIVLRVNSPggsvTASEVIRAELAAARaa-gKPVVV 376 Escherichia coli
CAM75754   57 GIAIVPVVGtlvarsgylgaasgltgYGDIADAIEAAATdpgvRAILLDVDSSggevGGLFDLVDHIQAIRsqcgKPIWA 136 Magnetospirillum g...
Feature 1            #                                                                        
3BF0_A    377 SMggMAASGGYWISTPanyIVANPSTLTGSIGIFGVittvensldsiGVHTDGVstsplADVSi--tRALPpeaQLMMQL 454 Escherichia coli
3BEZ_A    377 SXggXAASGGYWISTPanyIVANPSTLTGSIGIFGVittvensldsiGVHTDGVstsplADVSi--tRALPpeaQLXXQL 454 Escherichia coli
CAM75754  137 VAdeAALSAAYAIACTadrIYVTQTGEVGSIGVVAVhrdesgadaqaGLAWTFVha-gaAKVDgnphQPLSdsaRAGLQA 215 Magnetospirillum g...
Feature 1                                                               
CAM75754  216 DVDALYGRFVALVARcrkqpPEAIRATe-AAVYRGDQAVAAGLADKVgtlrVALADLG 272 Magnetospirillum gryphiswaldense MSR-1

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