Sortaseprocessed

Sortaseprocessed refers to proteins that have undergone sortase-mediated processing, a post-translational step in many Gram-positive bacteria that covalently anchors proteins to the cell wall. Sortases are transpeptidases that recognize sorting signals near the C terminus, most commonly the LPXTG motif, and catalyze a transpeptidation reaction that attaches the protein to the peptidoglycan.

Most sortase substrates are exported across the cytoplasmic membrane by the Sec pathway and present at the cell surface with a C-terminal sorting signal consisting of three parts: the LPXTG motif, a hydrophobic domain, and a short positively charged tail that anchors the protein in the membrane before sortase action. The enzyme cleaves between the T and G residues of LPXTG, forms a thioacyl intermediate with its active-site cysteine, and transfers the substrate to the amino group of the pentaglycine cross-bridge of peptidoglycan or to lipid II, thereby covalently linking the protein to the cell wall. The result is a mature, cell-wall–anchored protein.

Functionally, sortase-processed proteins include adhesins, enzymes, and virulence factors that mediate adherence to host tissues, biofilm formation, and immune interactions. Different sortase enzymes (such as SrtA, SrtB, SrtC) recognize distinct motifs and direct alternative assembly pathways, including pilus formation in some species.

In research and biotechnology, sortase-mediated ligation is exploited to display or modify proteins, enabling targeted anchoring of proteins to bacterial surfaces or the creation of defined protein conjugates. The term sortaseprocessed thus denotes maturation by this pathway.