Total chemical synthesis of glycocin F and analogues: -glycosylation confers improved antimicrobial activity.

Glycocin F (GccF) is a unique diglycosylated bacteriocin peptide that possesses potent and reversible bacteriostatic activity against a range of Gram-positive bacteria. GccF is a rare example of a 'glycoactive' bacteriocin, with both the -linked -acetylglucosamine (GlcNAc) and the unusual -linked GlcNAc moiety important for antibacterial activity. In this report, glycocin F was successfully prepared using a native chemical ligation strategy and folded into its native structure. The chemically synthesised glycocin appeared to be slightly more active than the recombinant material produced from . A second-generation synthetic strategy was used to prepare 2 site selective 'glyco-mutants' containing either two -linked or two -linked GlcNAc moieties; these mutants were used to probe the contribution of each type of glycosidic linkage to bacteriostatic activity. Replacing the -linked GlcNAc at residue 43 with an -linked GlcNAc decreased the antibacterial activity, while replacing -linked GlcNAc at position 18 with an -linked GlcNAc increased the bioactivity suggesting that the -glycosidic linkage may offer a biologically-inspired route towards more active bacteriocins.