Sortase domain found in class C sortases; Class C sortases are membrane-bound cysteine transpeptidases broadly distributed in Gram-positive bacteria (mainly present in Firmicutes and Actinobacteria). They function as pilin polymerases responsible for the assembly of pili, which are multi-subunit hair-like fibres that extend from the cell surface to promote microbial adhesion and biofilm formation. First, one or more class C sortases form the long thin shaft of the pilus through linking together pilin subunits via isopeptide bonds. The base of the pilus is then anchored to the cell wall by a housekeeping sortase or, in some cases, the class C sortase itself. Depending upon the organism both the number and type of sortase enzymes involved varies, and in some cases, accessory factors appear to be needed. In three-component spaA pilus from Corynebacterium diphtheriae, the prototypical class C sortase (named Cd-SrtA) catalyzes polymerization of the SpaA-type pilus, consisting of the shaft pilin SpaA, tip pilin SpaC and minor pilin SpaB. The pilus shaft is then attached to the cell wall by a housekeeping class E sortase, Cd-SrtF. In the absence of Cd-SrtF, Cd-SrtA attaches the pilus to the cell wall, albeit at a reduced rate. Cd-SrtA can recognize two distinct sorting signals (LPLTG in SpaA and SpaC, and LAFTG in SpaB) and it can employ lysine residues that originate from different proteins (either Lys190 within the pilin motif of SpaA or Lys139 in SpaB). However, Cd-SrtA cannot be able to polymerize the major pilin subunit SpaH, even though it contains LPLTG motif. In two-component pili of prototypical Bacillus cereus, the class C sortase (named Bc-SrtD) cleaves related sorting signals within a major pilin protein BcpA (LPVTG) and a minor tip pilin BcpB (IPNTG), and catalyzes a transpeptidation that joins the threonine residues in each signal to the side-chain of Lys162 in BcpA (located within a pilin motif). Unlike the SpaA pilus in C. diphtheriae, in B. cereus Bc-SrtD is unable to covalently attach the pilus to the cell wall without the help of the housekeeping sortase.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8GR6_A       82 TGIMAYVEIPKLGTNLPIYHGTDDAILQVAIGHIPGSSLPVGGQGTHSVISGHRGLPSAKLFTDIDKLKNGDRFMIHVLG 161
Cdd:cd05827   1 DGVIGYLEIPKIDVDLPIYHGTSEEVLAKGAGHLEGTSLPVGGKGTHSVIAGHRGLPNATLFTDLDKLKKGDKFYITVLG 80

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|.
8GR6_A      162 KTITYQVDQTLTVEPEDISSLAIDPDQDYCTLVTCTPYGINS*RLLVRGHR 212
Cdd:cd05827  81 ETLAYKVDDIKVILPDDTDKLKIQPGKDLVTLLTCTPYGINTHRLLVTGER 131

Sortase (surface protein transpeptidase) [Cell wall/membrane/envelope biogenesis];

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8GR6_A       82 TGIMAYVEIPKLGTNLPIYHGTDDAILQVAIGHIPGSSLPvgGQGTHSVISGHRGLPSAKLFTDIDKLKNGDRFMIHVLG 161
Cdd:COG3764  11 AGLIGRLEIPKIGVDLPIVEGTDEDTLAKGAGHYPGTALP--GEVGNAVLAGHRDTPGGTVFRRLDELKPGDEIYVETAD 88

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|....*..
8GR6_A      162 KTITYQVDQTLTVEPEDISSLAIDpDQDYCTLVTCTPYGINS*RLLVRGHRVPNEKN 218
Cdd:COG3764  89 GTYTYRVTSIEVVDPDDVEVLAPT-GKPLLTLITCTPFGSNTDRLIVYAELVSTTPK 144

Sortase domain found in class C sortases; Class C sortases are membrane-bound cysteine transpeptidases broadly distributed in Gram-positive bacteria (mainly present in Firmicutes and Actinobacteria). They function as pilin polymerases responsible for the assembly of pili, which are multi-subunit hair-like fibres that extend from the cell surface to promote microbial adhesion and biofilm formation. First, one or more class C sortases form the long thin shaft of the pilus through linking together pilin subunits via isopeptide bonds. The base of the pilus is then anchored to the cell wall by a housekeeping sortase or, in some cases, the class C sortase itself. Depending upon the organism both the number and type of sortase enzymes involved varies, and in some cases, accessory factors appear to be needed. In three-component spaA pilus from Corynebacterium diphtheriae, the prototypical class C sortase (named Cd-SrtA) catalyzes polymerization of the SpaA-type pilus, consisting of the shaft pilin SpaA, tip pilin SpaC and minor pilin SpaB. The pilus shaft is then attached to the cell wall by a housekeeping class E sortase, Cd-SrtF. In the absence of Cd-SrtF, Cd-SrtA attaches the pilus to the cell wall, albeit at a reduced rate. Cd-SrtA can recognize two distinct sorting signals (LPLTG in SpaA and SpaC, and LAFTG in SpaB) and it can employ lysine residues that originate from different proteins (either Lys190 within the pilin motif of SpaA or Lys139 in SpaB). However, Cd-SrtA cannot be able to polymerize the major pilin subunit SpaH, even though it contains LPLTG motif. In two-component pili of prototypical Bacillus cereus, the class C sortase (named Bc-SrtD) cleaves related sorting signals within a major pilin protein BcpA (LPVTG) and a minor tip pilin BcpB (IPNTG), and catalyzes a transpeptidation that joins the threonine residues in each signal to the side-chain of Lys162 in BcpA (located within a pilin motif). Unlike the SpaA pilus in C. diphtheriae, in B. cereus Bc-SrtD is unable to covalently attach the pilus to the cell wall without the help of the housekeeping sortase.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8GR6_A       82 TGIMAYVEIPKLGTNLPIYHGTDDAILQVAIGHIPGSSLPVGGQGTHSVISGHRGLPSAKLFTDIDKLKNGDRFMIHVLG 161
Cdd:cd05827   1 DGVIGYLEIPKIDVDLPIYHGTSEEVLAKGAGHLEGTSLPVGGKGTHSVIAGHRGLPNATLFTDLDKLKKGDKFYITVLG 80

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|.
8GR6_A      162 KTITYQVDQTLTVEPEDISSLAIDPDQDYCTLVTCTPYGINS*RLLVRGHR 212
Cdd:cd05827  81 ETLAYKVDDIKVILPDDTDKLKIQPGKDLVTLLTCTPYGINTHRLLVTGER 131

Sortase (surface protein transpeptidase) [Cell wall/membrane/envelope biogenesis];

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8GR6_A       82 TGIMAYVEIPKLGTNLPIYHGTDDAILQVAIGHIPGSSLPvgGQGTHSVISGHRGLPSAKLFTDIDKLKNGDRFMIHVLG 161
Cdd:COG3764  11 AGLIGRLEIPKIGVDLPIVEGTDEDTLAKGAGHYPGTALP--GEVGNAVLAGHRDTPGGTVFRRLDELKPGDEIYVETAD 88

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|....*..
8GR6_A      162 KTITYQVDQTLTVEPEDISSLAIDpDQDYCTLVTCTPYGINS*RLLVRGHRVPNEKN 218
Cdd:COG3764  89 GTYTYRVTSIEVVDPDDVEVLAPT-GKPLLTLITCTPFGSNTDRLIVYAELVSTTPK 144

Sortase domain found in subfamily 2 of the class D family of sortases; Class D sortases are cysteine transpeptidases distributed in Gram-positive bacteria (mainly present in Firmicutes). They anchor surface proteins bearing a cell wall sorting signal to peptidoglycans of the bacterial cell wall envelope, which is responsible for spore formation under anaerobic conditions. This involves a transpeptidation reaction in which the surface protein substrate is cleaved at the cell wall sorting signal and covalently linked to peptidoglycan for display on the bacterial surface. The prototypical subfamily 2 of class D sortase from Clostridium perfringens (named Cp-SrtD) recognizes the LPQTGS signal motif for transpeptidation. Its catalytic activity is in a metal cation- and temperature- dependent manner. The presence of magnesium appears to enhance Cp-SrtD catalysis towards the LPQTGS signal motif.

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                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8GR6_A       83 GIMAYVEIPKLGTNLPIYHGTDDAILQVAIGHIPGSSLPvgGQGTHSVISGHRGLPSAKLFTDIDKLKNGDRFMIHVLGK 162
Cdd:cd06166   2 GVIGILEIPKIDLKLPILEGATEENLKYGVGHFEGTAMP--GEGGNFAIAGHRSYTYGRFFNRLDELKIGDEIIVTTKNG 79

                        90       100       110       120
                ....*....|....*....|....*....|....*....|....*...
8GR6_A      163 TITYQVDQTLTVEPEDISSLAIDPDQDYCTLVTCTPyGINS*RLLVRG 210
Cdd:cd06166  80 TYTYKVTEIFIVEPTDVSVLDPTEGKKEITLITCTP-INPTHRLIVKA 126

Sortase domain found in the class E family of sortases; Class E sortases are membrane-bound cysteine transpeptidases distributed in Gram-positive bacteria (mainly present in Actinobacteria). Genes encoding class A and E sortases are never found in the same organism, and similar to class A sortases, the genes encoding class E sortases are not positioned adjacent to genes encoding potential protein substrates, suggesting a housekeeping sortase function of class E sortases in some high G + C Gram-positive bacteria. Similar to class A sortase, class E sortases are capable of anchoring a large number of functionally distinct surface proteins containing a cell wall sorting signal to an amino group located on the bacterial cell wall. They recognize an LAXTG sorting signal, instead of the canonical LPXTG motif processed by class A sortases. The prototypical class E sortase from Corynebacterium diphtheria (named Cd-SrtF) is a non-polymerization sortase that is not required for pilus polymerization, and proceeds to complete the assembly process by anchoring the polymer to the cell wall peptidoglycan. Moreover, in Streptomyces coelicolor, one or both of Staphylococcus aureus SrtA homologs may function as class E sortase responsible for the cell wall anchoring of the long chaplin proteins (ChpA-C) containing an LAXTG sorting signal, which presumably mediate aerial hyphae formation. The family also includes some class E sortase homologs from Gram-negative and Archaebacterial species, but the functions of these enzymes are unknown.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8GR6_A       85 MAYVEIPKL-GTNLPIYHGTDDAILQVAIGHIPGSSLPvgGQGTHSVISGHR---GLPsaklFTDIDKLKNGDRFMIHVL 160
Cdd:cd05830   4 FAVLYIPRFiDLDRPVVEGTSEVLLRRGVGHYPGTALP--GEVGNFAIAGHRttyGAP----FRDLDELRPGDPIVVETA 77

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|....*...
8GR6_A      161 GKTITYQVDQTLTVEPEDISSLAI-------DPDQDYCTLVTCTPYGINS*RLLVRGH 211
Cdd:cd05830  78 GGWYVYRVTSTEIVSPDDVEVLAPvpgqpgaPPGRRLLTLTTCHPPGSSAERLIVHAE 135

Sortase domain found in class A sortases; Class A sortases are membrane-bound cysteine transpeptidases distributed in Gram-positive bacteria (mainly present in Firmicutes). They perform a housekeeping role in the cell as members of this group are capable of anchoring a large number of functionally distinct surface proteins containing a cell wall sorting signal to an amino group located on the bacterial cell wall. They do so by catalyzing a transpeptidation reaction in which the surface protein substrate is cleaved at a conserved cell wall-sorting signal (Class A sortases recognize a canonical LPXTG motif, X can be any amino acid), and covalently linked to peptidoglycan for display on the bacterial surface. The prototypical sortase A protein from Staphylococcus aureus (named Sa-SrtA) cleaves the amide bond between threonine and glycine residues of the canonical LPXTG motif in a wide range of protein substrates with diverse functions that can promote bacterial adhesion, nutrient acquisition, host cell invasion, and immune evasion. Next, it catalyzes a transpeptidation reaction by which the proteins are covalently linked to the peptidoglycan precursor lipid II. SrtA is therefore affects the ability of a pathogen to establish successful infection. SrtA contains an N-terminal hydrophobic segment, a linker region and an extra-cellular C-terminal catalytic domain. The hydrophobic segment functions as both a signal peptide for secretion and a stop-transfer signal for membrane anchoring. The catalytic domain contains the catalytic TLXTC signature sequence where X is usually a valine, isoleucine or a threonine. The gene encoding SrtA is generally not located in the same gene cluster as its substrates while the gene encoding SrtB is usually clustered in the same locus as its substrate.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8GR6_A       84 IMAYVEIPKLGTNLPIYHGTDDAILQVAIGHI-PGSSLpvgGQGtHSVISGHRgLPSAK-LFTDIDKLKNGDRFMIHVLG 161
Cdd:cd06165   3 VIGAIAIPSVGINLPIFKGLSNENLLVGAGTMkPNQKM---GKG-NYVLAGHN-MGDGGlLFSPLQNLKKGDKIYLTDLK 77

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|
8GR6_A      162 KTITYQVDQTLTVEPEDISSLAIDPDQDYCTLVTCTPYGINS*RLLVRGH 211
Cdd:cd06165  78 KVYEYKVTSKKVVDPTDVDVLDDTKGKPLLTLITCDDPTDTTKRIVVQGE 127