Common mechanisms of target cell recognition and immunity for class II bacteriocins.
The mechanisms of target cell recognition and producer cell self-protection (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.
Diep
Dzung B
DB
Laboratory of Microbial Gene Technology, Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Science, N-1432 As, Norway. dzung.diep@umb.no
Skaugen
Morten
M
Salehian
Zhian
Z
Holo
Helge
H
Nes
Ingolf F
IF
D001419:Bacteria / Q000276:immunology; D001430:Bacteriocins / Q000276:immunology* / Q000378:metabolism; D007109:Immunity; D013294:Lactococcus lactis / Q000276:immunology / Q000472:pathogenicity*; D008565:Membrane Proteins / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000276:immunology; D046912:Multiprotein Complexes; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism; D011485:Protein Binding
D001430:Bacteriocins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C069325:lactococcin A; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C037992:phosphoenolpyruvate-mannose phosphotransferase