Site-specific N- and C-terminal labeling of a single polypeptide using sortases of different specificity

Abstract

(Figure Presented) The unique reactivity of two sortase enzymes, SrtA staph from Staphylococcus aureus and SrtAstrep from Streptococcus pyogenes, is exploited for site-specific labeling of a single polypeptide with different labels at its N and C termini. SrtAstrep is used to label the protein's C terminus at an LPXTG site with a fluorescently labeled dialanine nucleophile. Selective N-terminal labeling of proteins containing N-terminal glycine residues is achieved using SrtAstaph and LPXT derivatives. The generality of N-terminal labeling with SrtA staph is demonstrated by near-quantitative labeling of multiple protein substrates with excellent site specificity. © 2009 American Chemical Society.