The glycocins: in a class of their own

First reported in 2011, glycocins (glycosylated bacteriocins) are bacterial toxins that constitute a subset of ribosomally synthesised and post-translationally modified peptide (RiPP) natural products. Three NMR structures (glycocin F, ASM1 and sublancin 168), two with helix-loop-helix Cs alpha/alpha folds, are deposited in the PDB. Each structure contains a monosaccharide beta-S-linked to a cysteine side chain. Three more glycocins (thurandacin, and enterocins F4-9 and 96) have been biochemically characterised, and others predicted on the basis of bioinformatic analyses. Only glycocin F, ASM1 and enterocin F4-9 are unequivocally glycoactive. This review probes the structure-function relationships of four types of nested disulfide-bonded glycocins.