title: Distribution of the NisI immunity protein and enhancement of nisin activity by the lipid-free NisI.
abstract: Lactococcus lactis cells producing the antibacterial peptide nisin protect their own cytoplasmic membrane by specific immunity proteins, NisI and NisF/E/G. We show here that approximately half of the produced NisI escaped the lipid modification (LF-NisI=lipid-free NisI) and was secreted to the medium, and that LF-NisI had no affinity to cells of L. lactis. The molar ratio of NisI and nisin was determined to be approximately 1:10 on the cell surface and 1:50 in the culture supernatant. Purified LF-NisI was shown to enhance the activity of nisin against several tested indicator strains. The enhancement of nisin activity by LF-NisI was not observed with cells containing the NisFEG transport system.
authors.affiliation: Department of Applied Chemistry and Microbiology, Viikki Biocenter, P.O. Box 56, 00014 University of Helsinki, Finland.
authors.forename: Olli
authors.initials: O
authors.lastname: Koponen
authors.forename: Timo M
authors.initials: TM
authors.lastname: Takala
authors.forename: Ulla
authors.initials: U
authors.lastname: Saarela
authors.forename: Mingqiang
authors.initials: M
authors.lastname: Qiao
authors.forename: Per E J
authors.initials: PE
authors.lastname: Saris
mesh_terms: D001426:Bacterial Proteins / Q000276:immunology / Q000378:metabolism*; D013294:Lactococcus lactis / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008074:Lipoproteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D009561:Nisin / Q000235:genetics / Q000276:immunology* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; C094909:NisI protein, Lactococcus lactis; D009561:Nisin