Glycocin F: a bacteriostatic, glycosylated bacteriocin

Bisset SW1,3, Amso Z2, Yang SH2, Brimble MA2,3, Patchett ML1 and Norris GE1,3

  1. Institute of Fundamental Sciences, Massey University, Colombo Rd, Palmerston North 4442, New Zealand.
  2. School of Chemical Sciences, The University of Auckland, 23 Symonds St, Auckland 1142, New Zealand.
  3. Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, New Zealand.

Bacteriocins are a class of bacterial peptides that inhibit the growth of closely-related strains or species of bacteria. Glycocin F (GccF) is a glycosylated, 43 amino acid bacteriocin (glycocin) produced by a strain of the probiotic bacteria Lactobacillus plantarum. GccF contains two N-acetylglucosamine (GlcNAc) moieties required for full anti-bacterial activity, one O-linked through serine 18, and the other S-linked through the C-terminal cysteine 43 at the end of a flexible tail. Two nested disulfide bonds are also required for activity. Whereas most bacteriocins exhibit bactericidal effects on a narrow range of species, GccF displays a potent, immediate and reversible bacteriostatic activity towards a range of Gram positive bacteria, and at least one Gram negative strain, making it a potentially useful tool for combating antibiotic resistant bacteria. Although a GlcNAc-specific phosphoenolpyruvate:sugar phosphotransferase system (PTS) EIIC domain has been shown to be one target, there is evidence that another target may be involved. In order to understand how GccF works, we have chemically synthesised a number of GccF analogues designed to probe structure-activity relationships, have used genetic engineering techniques to probe potential receptor-GccF interactions, and are currently investigating the structure of one particularly interesting analogue using NMR. A transcriptomic study of susceptible cells has also been carried out in the absence and presence of GccF in an effort to narrow down the pathways exploited by GccF. These results will be presented, along with a model for the mechanism of action that best fits the data we have collected thus far.