sortasedependent

Sortase-dependent refers to a set of cell-surface proteins in Gram-positive bacteria that are covalently anchored to the cell wall by sortase enzymes. These proteins typically contain an N-terminal signal sequence and a C-terminal LPXTG sorting motif recognized by sortases, and they function as adhesins, enzymes, or structural components on the bacterial surface.

Mechanism and diversity: The best-studied member, sortase A, cleaves the LPXTG motif between the threonine and glycine, forming a thioacyl intermediate. The substrate is then transferred to the amino group of peptidoglycan cross-bridges, resulting in covalent attachment to the cell wall. Other sortase classes mediate specialized tasks, such as pilus assembly (notably class C sortases) or substrate-specific functions (other classes B, D, etc.). This system enables a broad repertoire of surface proteins that mediate interactions with the host and the environment.

Biological role: Sortase-dependent proteins contribute to adhesion to host tissues, biofilm formation, colonization, and immune interactions. They are frequently implicated in virulence in pathogenic Gram-positive bacteria. Examples include adhesins such as clumping factor A and protein A in Staphylococcus aureus, and M proteins in Streptococcus species, which are anchored to the cell wall via sortase activity.

Applications and relevance: Sortase enzymes are widely used in biotechnology for protein display and covalent labeling of proteins or peptides (sortagging), enabling surface engineering of bacteria or other substrates. In medicine, SDPs are studied as targets for vaccines and anti-virulence therapies.