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:
Feature 1                                                                  #                  
1QX6_A     39 KDIVGWIKLSgtSLNYPVLQgktnhdylnldferehrrkgSIFXDFrnelknlnHNTILYGHHVgd--ntXFDVLEDYlk 116 Staphylococcus aureus
1T2W_A      9 SKVAGYIEIPdaDIKEPVYPgpatp----------eqlnrGVSFAEenes-lddQNISIAGHTFidrpnyQFTNLKAAk- 76  Staphylococcus aureus
CCY45033   23 NDDKDIIEISsiNINLEYSIssin------------dsviGIVMFSeygr-pdqNNAIIGAHSGygp-naYFNDLDKLe- 87  Clostridium sp. CA...
CDE38437   37 YSENISLIIPsiNFSKTFDNnstlk----------nnlelEKSSVMpne---enSTVIILGHSGynf-naYFNDLFDLk- 101 Mycoplasma sp. CAG...
1NG5_A     40 KDIVGWIKLSgtSLNYPVLQgktnhdylnldferehrrkgSIFMDFrnelknlnHNTILYGHHVgd--ntMFDVLEDYlk 117 Staphylococcus aur...
1QWZ_A     60 KDIVGWIKLSgtSLNYPVLQgktnhdylnldferehrrkgSIFMDFrnelknlnHNTILYGHHVgd--ntMFDVLEDYlk 137 Staphylococcus aureus
4LFD_A     41 KDIVGWIKLSgtSLNYPVLQgktnhdylnldferehrrkgSIFMDFrnelknlnHNTILYGHHVgd--ntMFDVLEDYlk 118 Staphylococcus aur...
1RZ2_A     79 QEIVGWITMDdtQINYPIVQakdndyylfrnykgedmragSIFMDYrndvksqnRNTILYGHRMkd--gsMFGSLKKMld 156 Bacillus anthracis...
2OQW_A     48 QEIVGWITXDdtQINYPIVQakdndyylfrnykgedxragSIFXDYrndvksqnRNTILYGHRXkd--gsXFGSLKKXld 125 Bacillus anthracis...
3PSQ_A     34 SDVMAWLTVKgtHIDYPIVQgennleyinksvegeyslsgSVFLDYrnkvtfedKYSLIYAHHMag--nvMFGELPNFrk 111 Streptococcus pyog...
Feature 1                                                                                   # 
1QX6_A    117 qsfyekHKIIEFDNk-yGKYQLQVFSAYKTttkdnyirtdfendqdyqqf-ldetkrksvinsdvnvtvkDRIXTLSTCE 194 Staphylococcus aureus
1T2W_A     77 -----kGSMVYFKVg-nETRKYKMTSIRDVkptdvgv--------------------------ldeqkgkDKQLTLITAD 124 Staphylococcus aureus
CCY45033   88 -----sGDLIKLIYd-gVTYKYLVSEVFEVddtsie-----------------------------vldssYEGLILITCK 132 Clostridium sp. CA...
CDE38437  102 -----kGDFIYLKYl-gKTYTYKVFEIEYInknefy-----------------------------kvqynKNYLYLVTCD 146 Mycoplasma sp. CAG...
1NG5_A    118 qsfyekHKIIEFDNk-yGKYQLQVFSAYKTttkdnyirtdfendqdyqqf-ldetkrksvinsdvnvtvkDKIMTLSTCE 195 Staphylococcus aur...
1QWZ_A    138 qsfyekHKIIEFDNk-yGKYQLQVFSAYKTttkdnyirtdfendqdyqqf-ldetkrksvinsdvnvtvkDRIMTLSTCE 215 Staphylococcus aureus
4LFD_A    119 qsfyekHKIIEFDNk-yGKYQLQVFSAYKTttkdnyirtdfendqdyqqf-ldetkrksvinsdvnvtvkDRIMTLSTCE 196 Staphylococcus aur...
1RZ2_A    157 eeffmsHRKLYYDTl-fEGYDLEVFSVYTTttdfyyietdfssdteytsf-lekiqekslyktdttvtagDQIVTLSTCD 234 Bacillus anthracis...
2OQW_A    126 eeffxsHRKLYYDTl-fEGYDLEVFSVYTTttdfyyietdfssdteytsf-lekiqekslyktdttvtagDQIVTLSTXD 203 Bacillus anthracis...
3PSQ_A    112 ksffnkHKEFSIETktkQKLKINIFACIQTdafdsllfnpidvdisskneflnhikqksvqyreilttneSRFVALSTCE 191 Streptococcus pyog...
Feature 1                #      
1QX6_A    195 days---ettKRIVVVAK 209 Staphylococcus aureus
1T2W_A    125 dynektgvweKRKIFVAT 142 Staphylococcus aureus
CCY45033  133 vgd-----dsKRIVVKAS 145 Clostridium sp. CAG:1193
CDE38437  147 lyn-----fsKQIVIKSS 159 Mycoplasma sp. CAG:472
1NG5_A    196 days---ettKRIVVVAK 210 Staphylococcus aureus subsp. aureus N315
1QWZ_A    216 days---ettKRIVVVAK 230 Staphylococcus aureus
4LFD_A    197 days---ettKRIVVVAK 211 Staphylococcus aureus subsp. aureus USA300
1RZ2_A    235 yald---peaGRLVVHAK 249 Bacillus anthracis str. Ames
2OQW_A    204 yald---peaGRLVVHAK 218 Bacillus anthracis str. Ames
3PSQ_A    192 dmt-----tdGRIIVIGQ 204 Streptococcus pyogenes serotype M1

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