Common mechanisms of target cell recognition and immunity for class II bacteriocins

Abstract

The mechanisms of target cell recognition and producer cell selfprotection (immunity) are both important yet poorly understood issues in the biology of peptide bacteriocins. In this report, we provide genetic and biochemical evidence that lactococcin A, a permeabilizing peptide-bacteriocin from Lactococcus lactis, uses components of the mannose phosphotransferase system (man-PTS) of susceptible cells as target/receptor. We present experimental evidence that the immunity protein LciA forms a strong complex with the receptor proteins and the bacteriocin, thereby preventing cells from being killed. Importantly, the complex between LciA and the man-PTS components (IIAB, IIC, and IID) appears to involve an on-off type mechanism that allows complex formation only in the presence of bacteriocin; otherwise no complexes were observed between LciA and the receptor proteins. Deletion of the man-PTS operon combined with biochemical studies revealed that the presence of the membrane-located components IIC and IID was sufficient for sensitivity to lactococcin A as well as complex formation with LciA. The cytoplasmic component of the man-PTS, IIAB, was not required for the biological sensitivity or for complex formation. Furthermore, heterologous expression of the lactococcal man-PTS operon rendered the insensitive Lactobacillus sakei susceptible to lactococcin A. We also provide evidence that, not only lactococcin A, but other class II peptide-bacteriocins including lactococcin B and some Listeria-active pediocin-like bacteriocins also target the man-PTS components IIC and IID on susceptible cells and that their immunity proteins involve a mechanism in producer cell self-protection similar to that observed for LciA.antimicrobial peptides ͉ Mannose-PTS ͉ receptor ͉ protein complex ͉ coprecipitation

Genetic characterisation and heterologous expression of leucocin C, a class IIa bacteriocin from Leuconostoc carnosum 4010

“…In this group, bacteriocins, such as leucocin A (LeuA) (Hastings et al 1991), mesentericin Y105 (Hechard et al 1992) and pediocin (Henderson et al 1992;Marugg et al 1992;Nieto Lozano et al 1992) have very similar amino acid sequences and contain conserved YGNGV/L "pediocin box" motif and a Cterminal disulfide bridge formed by two cysteines. According to sequence similarities in the C-terminal region, IIa bacteriocins may be further sorted into three or four subgroups Nissen-Meyer et al 2009 (Holo et al 1991;Diep et al 2007). (Cotter et al 2005a).…”

Structure analysis of the two-peptide bacteriocin lactococcin G by introducing d-amino acid residues

“…It has been shown that the pediocin-like bacteriocins and the one-peptide bacteriocin lactococcin A bind to a part of the mannose phosphotransferase (man-PTS) system that is embedded in the cell membrane, thereby apparently structurally perturbing the transferase in a manner that leads to membrane leakage (Diep et al, 2007). It has also been shown that the cognate immunity protein recognizes and binds to the bacteriocin-man-PTS complex, and thereby prevents bacteriocin-induced cell death.…”

“…The immunity proteins for lactococcin A and the pediocin-like bacteriocins apparently recognize structural perturbations induced in their receptor (i.e. the man-PTS) upon binding of the bacteriocin to the receptor, and this in turn leads to binding of the immunity protein to the bacteriocinreceptor complex (Diep et al, 2007). The recognition of these bacteriocins by their immunity proteins appears therefore to be indirect (by way of the bacteriocin receptor), and the regions in these bacteriocins that are recognized by their receptor and their immunity proteins are thus apparently one and the same.…”

Scope of Bacteriocins as a Viable Alternative to the Traditional Antibiotics

“…Class II bacteriocins are large and highly diverse group of unmodified peptides with disulphide bridges are crucial for defining the 3-D conformations. They affect target cells in similar ways as class I bacteriocins, but their receptors seem to be proteins rather than lipids [11]. Class III bacteriocins are not peptides but heat-labile proteins.…”