The Glycosyltransferase Involved in Thurandacin Biosynthesis Catalyzes Both O- and S‑Glycosylation

Abstract

The S-glycosyltransferase SunS is a recently discovered enzyme that selectively catalyzes the conjugation of carbohydrates to the cysteine thiol of proteins. This study reports the discovery of a second S-glycosyltransferase, ThuS, and shows that ThuS catalyzes both S-glycosylation of the thiol of cysteine and O-glycosylation of the hydroxyl group of serine in peptide substrates. ThuS-catalyzed S-glycosylation is more efficient than O-glycosylation, and the enzyme demonstrates high tolerance with respect to both nucleotide sugars and peptide substrates. The biosynthesis of the putative products of the <i>thuS</i> gene cluster was reconstituted <i>in vitro</i>, and the resulting S-glycosylated peptides thurandacin A and B exhibit highly selective antimicrobial activity toward <i>Bacillus thuringiensis.</i