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.