Sortase B family (IPR009835)

Short name: SrtB

Overlapping homologous superfamilies

Family relationships


Members of this transpeptidase family are, in most cases, designated sortase B, product of the srtB gene. This protein shows only distant similarity to the sortase A family, for which there may be several members in a single bacterial genome. Typical SrtB substrate motifs include NAKTN, NPKSS, etc, and otherwise resemble the LPXTG sorting signals recognised by sortase A proteins.

Sortase B sortases are membrane cysteine transpeptidases found in Gram-positive bacteria that anchor surface proteins to peptidoglycans of the bacterial cell wall envelope [PMID: 15028680, PMID: 16524923]. This involves 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 and subfamilies based on sequence, membrane topology, genomic positioning, and cleavage site preference [PMID: 15808931]. Sortase B cleaves surface protein precursors between threonine and asparagine at a conserved NPQTN motif with subsequent covalent linkage to peptidoglycan [PMID: 17200112]. It is required for anchoring the heme-iron binding surface protein IsdC to the cell wall envelope and the gene encoding Sortase B is located within the isd locus in S. aureus [PMID: 15718231, PMID: 14725770, PMID: 11401711] and B. anthracis [PMID: 17012401]. It may also play a role in pathogenesis [PMID: 16041044]. Sortase B contains an N-terminal region that functions as both a signal peptide for secretion and a stop-transfer signal for membrane anchoring. At the C terminus, it contains the catalytic TLXTC signature sequence, where X is usually a serine [PMID: 15242591]. Genes encoding SrtB and its targets are generally clustered in the same locus.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.