title: Peptide-lipid huge toroidal pore, a new antimicrobial mechanism mediated by a lactococcal bacteriocin, lacticin Q.
abstract: Lacticin Q is a pore-forming bacteriocin produced by Lactococcus lactis QU 5, and its antimicrobial activity is in the nanomolar range. Lacticin Q induced calcein leakage from negatively charged liposomes. However, no morphological changes in the liposomes were observed by light scattering. Concomitantly with the calcein leakage, lacticin Q was found to translocate from the outer to the inner leaflet of the liposomes, after it initially bound to the membrane within 2 s. Lacticin Q also induced lipid flip-flop. These results reveal that the antimicrobial mechanism of lacticin Q can be described by the toroidal pore model. This is the first report of a bacteriocin of gram-positive bacteria that forms a toroidal pore. From liposomes, lacticin Q leaked fluorescence-labeled dextran with a diameter of 4.6 nm. In addition, lacticin Q caused the leakage of small proteins, such as the green fluorescent protein, from live bacterial cells. There are no other reports of antimicrobial peptides that exhibit protein leakage properties. The proposed pore formation model of lacticin Q is as follows: (i) quick binding to outer membrane leaflets; (ii) the formation of at least 4.6-nm pores, causing protein leakage with lipid flip-flop; and (iii) the migration of lacticin Q molecules from the outer to the inner membrane leaflets. Consequently, we termed the novel pore model in the antimicrobial mechanism of lacticin Q a "huge toroidal pore."
authors.affiliation: Laboratory of Microbial Technology, Division of Microbial Science and Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Fuminori
authors.initials: F
authors.lastname: Yoneyama
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Imura
authors.forename: Kanako
authors.initials: K
authors.lastname: Ohno
authors.forename: Takeshi
authors.initials: T
authors.lastname: Zendo
authors.forename: Jiro
authors.initials: J
authors.lastname: Nakayama
authors.forename: Katsumi
authors.initials: K
authors.lastname: Matsuzaki
authors.forename: Kenji
authors.initials: K
authors.lastname: Sonomoto
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry*; D001430:Bacteriocins / Q000737:chemistry*; D013294:Lactococcus lactis / Q000378:metabolism*; D008055:Lipids / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*
chemical_list: D000890:Anti-Infective Agents; D001430:Bacteriocins; D008055:Lipids; D008081:Liposomes; D010455:Peptides