Conserved Protein Domain Family

cd00004: Sortase 
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Sortase domain
Sortases are cysteine transpeptidases, mainly found in Gram-positive bacteria, which either anchor surface proteins to peptidoglycans of the bacterial cell wall envelope or link proteins together to form pili by working alone, or in concert with other enzymes. They do so by catalyzing a transpeptidation reaction in which the surface protein substrate is cleaved at a conserved cell wall sorting signal and covalently linked to peptidoglycan for display on the bacterial surface. Sortases are grouped into different classes based on sequence, membrane topology, genomic positioning, and cleavage site preference. The different classes are called class A to F sortases. Most Gram-positive bacteria contain more than one sortase and it is thought that the different sortases attach different surface protein classes. The typical eight-stranded beta-barrel fold is observed in all known sortases, along with the conserved catalytic triad consisting of cysteine, histidine and arginine residues. Some sortases contain an N-terminal signal peptide only and the C-terminus serves as a membrane anchor, which represents a type I membrane topology, with the N-terminal enzymatic portion projecting towards the bacterial surface and the C-terminal end residing in the cytoplasm. Other sortases adopt a type II membrane topology, with the N-terminal hydrophobic segment inside the cytoplasm and the C-terminal enzymatic portion located across the plasma membrane. The N-terminus either functions as both a signal peptide for secretion and a stop-transfer signal for membrane anchoring. Sortases are also present in some Gram-negative and Archaebacterial species, but the functions of these enzymes are unknown.
PSSM-Id: 320674
View PSSM: cd00004
Aligned: 141 rows
Threshold Bit Score: 57.2065
Threshold Setting Gi: 765674877
Created: 4-Sep-2001
Updated: 18-Aug-2016
Aligned Rows:
Conserved site includes 3 residues -Click on image for an interactive view with Cn3D
Feature 1:catalytic site [active site]
  • Comment:The SrtA enzymes recognize a conserved five amino acid sequence (LPXTG) at the C-terminus of their protein substrates and cleave the amide bond between the threonine and glycine residues using a highly-conserved cysteine residue in the active site. Two other active site residues have been identified as essential for optimal enzyme activity, a His side-chain which serves as a general base and an Arg side-chain which stabilises the oxoanion intermediate formed during the reaction.
  • Comment:The catalytic triad is formed by His, Cys, and Arg. The sulfhydryl of Cys is ionized by His and the resultant thiolate attacks the LPXTG peptide.

Sequence Alignment
Format: Row Display: Color Bits: Type Selection:
                         10        20        30        40        50        60        70        80
Feature 1                                                                     #                  
1QX6_A        39 KDIVGWIKLSgtSLNYPVLQgktnhdylnldferehrrkgSIFXDFrnelknlnHNTILYGHHVgd--ntXFDVLEDYlk 116
1T2W_A         9 SKVAGYIEIPdaDIKEPVYPgpatp----------eqlnrGVSFAEenes-lddQNISIAGHTFidrpnyQFTNLKAAk- 76
gi 524065133  23 NDDKDIIEISsiNINLEYSIssin------------dsviGIVMFSeygr-pdqNNAIIGAHSGygp-naYFNDLDKLe- 87
gi 524735955  37 YSENISLIIPsiNFSKTFDNnstlk----------nnlelEKSSVMpne---enSTVIILGHSGynf-naYFNDLFDLk- 101
1NG5_A        40 KDIVGWIKLSgtSLNYPVLQgktnhdylnldferehrrkgSIFMDFrnelknlnHNTILYGHHVgd--ntMFDVLEDYlk 117
1QWZ_A        60 KDIVGWIKLSgtSLNYPVLQgktnhdylnldferehrrkgSIFMDFrnelknlnHNTILYGHHVgd--ntMFDVLEDYlk 137
4LFD_A        41 KDIVGWIKLSgtSLNYPVLQgktnhdylnldferehrrkgSIFMDFrnelknlnHNTILYGHHVgd--ntMFDVLEDYlk 118
1RZ2_A        79 QEIVGWITMDdtQINYPIVQakdndyylfrnykgedmragSIFMDYrndvksqnRNTILYGHRMkd--gsMFGSLKKMld 156
2OQW_A        48 QEIVGWITXDdtQINYPIVQakdndyylfrnykgedxragSIFXDYrndvksqnRNTILYGHRXkd--gsXFGSLKKXld 125
3PSQ_A        34 SDVMAWLTVKgtHIDYPIVQgennleyinksvegeyslsgSVFLDYrnkvtfedKYSLIYAHHMag--nvMFGELPNFrk 111
                         90       100       110       120       130       140       150       160
Feature 1                                                                                      # 
1QX6_A       117 qsfyekHKIIEFDNk-yGKYQLQVFSAYKTttkdnyirtdfendqdyqqf-ldetkrksvinsdvnvtvkDRIXTLSTCE 194
1T2W_A        77 -----kGSMVYFKVg-nETRKYKMTSIRDVkptdvgv--------------------------ldeqkgkDKQLTLITAD 124
gi 524065133  88 -----sGDLIKLIYd-gVTYKYLVSEVFEVddtsie-----------------------------vldssYEGLILITCK 132
gi 524735955 102 -----kGDFIYLKYl-gKTYTYKVFEIEYInknefy-----------------------------kvqynKNYLYLVTCD 146
1NG5_A       118 qsfyekHKIIEFDNk-yGKYQLQVFSAYKTttkdnyirtdfendqdyqqf-ldetkrksvinsdvnvtvkDKIMTLSTCE 195
1QWZ_A       138 qsfyekHKIIEFDNk-yGKYQLQVFSAYKTttkdnyirtdfendqdyqqf-ldetkrksvinsdvnvtvkDRIMTLSTCE 215
4LFD_A       119 qsfyekHKIIEFDNk-yGKYQLQVFSAYKTttkdnyirtdfendqdyqqf-ldetkrksvinsdvnvtvkDRIMTLSTCE 196
1RZ2_A       157 eeffmsHRKLYYDTl-fEGYDLEVFSVYTTttdfyyietdfssdteytsf-lekiqekslyktdttvtagDQIVTLSTCD 234
2OQW_A       126 eeffxsHRKLYYDTl-fEGYDLEVFSVYTTttdfyyietdfssdteytsf-lekiqekslyktdttvtagDQIVTLSTXD 203
3PSQ_A       112 ksffnkHKEFSIETktkQKLKINIFACIQTdafdsllfnpidvdisskneflnhikqksvqyreilttneSRFVALSTCE 191
Feature 1                   #      
1QX6_A       195 days---ettKRIVVVAK 209
1T2W_A       125 dynektgvweKRKIFVAT 142
gi 524065133 133 vgd-----dsKRIVVKAS 145
gi 524735955 147 lyn-----fsKQIVIKSS 159
1NG5_A       196 days---ettKRIVVVAK 210
1QWZ_A       216 days---ettKRIVVVAK 230
4LFD_A       197 days---ettKRIVVVAK 211
1RZ2_A       235 yald---peaGRLVVHAK 249
2OQW_A       204 yald---peaGRLVVHAK 218
3PSQ_A       192 dmt-----tdGRIIVIGQ 204

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