Structural, Dynamic, and Chemical Characterization of a Novel S-Glycosylated Bacteriocin

Abstract

Bacteriocins are bacterial peptides with specific activity against competing species. They hold great potential as natural preservatives and for their probiotic effects. We show here nuclear magnetic resonance-based evidence that glycocin F, a 43-amino acid bacteriocin from Lactobacillus plantarum, contains two β-linked N-acetylglucosamine moieties, attached via side chain linkages to a serine via oxygen, and to a cysteine via sulfur. The latter linkage is novel and has helped to establish a new type of post-translational modification, the S-linked sugar. The peptide conformation consists primarily of two α-helices held together by a pair of nested disulfide bonds. The serine-linked sugar is positioned on a short loop sequentially connecting the two helices, while the cysteine-linked sugar presents at the end of a long disordered C-terminal tail. The differing chemical and conformational stabilities of the two N-actetylglucosamine moieties provide clues about the possible mode of action of this bacteriostatic peptide.