Transpeptidase that anchors surface proteins to the cell wall (PubMed:10427003, PubMed:10446208, PubMed:10535938, PubMed:11714722, PubMed:14769030, PubMed:15247224). Recognizes and modifies its substrate by proteolytic cleavage of a C-terminal sorting signal. Following cleavage, a covalent intermediate is formed via a thioester bond between the sortase and its substrate, which is then transferred and covalently attached to the cell wall (PubMed:10446208, PubMed:10535938, PubMed:11714722, PubMed:14769030, PubMed:15247224). This sortase recognizes a Leu-Pro-x-Thr-Gly (LPXTG) motif, which is cleaved by the sortase between the threonine and glycine residues (PubMed:10535938, PubMed:11714722, PubMed:14769030, PubMed:15247224). Utilizes lipid II as the peptidoglycan substrate for the sorting reaction (PubMed:10446208, PubMed:11856734). Responsible for the display of important virulence factors (PubMed:14769030). Important for interactions with the host and host colonization during infection (PubMed:10805806, PubMed:14769030). The enzyme catalyzes a cell wall sorting reaction in which a surface protein with a sorting signal containing a LPXTG motif is cleaved between the Thr and Gly residue. The resulting threonine carboxyl end of the protein is covalently attached to a pentaglycine cross-bridge of peptidoglycan. Sortase activity is regulated by monomer-homodimer equilibrium. Mutant cells with monomeric SrtA display more adhesive proteins on the cell surface and are more invasive than wild-type cells, which have majority of SrtA in dimeric form. Dimerization may suppress the enzymatic activity on cell membranes (PubMed:26129884). Stimulated by calcium ions, which promote substrate binding (PubMed:11371637, PubMed:16269411). Calcium ions bind to SrtA and modulate both the structure and dynamics of a large active site loop (PubMed:16269411). Can also be stimulated, to a lesser extent, by Mg(2+) and Mn(2+) (PubMed:11371637). Inhibited by sulfhydryl-modifying reagents (PubMed:10535938, PubMed:10446208). Monomer and homodimer; in equilibrium. Mutants fail to cleave and anchor surface proteins (PubMed:10427003, PubMed:10805806). Protein secretion pathway is not affected (PubMed:10805806). Mutants are defective in the establishment of animal infections (PubMed:10805806). Could be used as a target for the development of antivirulence chemotherapeutics against Gram-positive bacterial pathogens. Belongs to the bacterial sortase family. Class A subfamily.