Functional analysis of sortase B reveals key residues for catalytic activity and substrate specificity.

Most of Gram-positive bacteria anchor surface proteins to the peptidoglycan cell wall by sortase, a cysteine transpeptidase that targets proteins displaying a cell wall sorting signal. Unlike other bacteria, , the major human pathogen responsible for antibiotic-associated diarrhea, has only a single functional sortase (SrtB). Sortase's vital importance in bacterial virulence has been long recognized, and sortase B (Cd-SrtB) has become an attractive therapeutic target for managing infection.