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Antimicrobial Agents and Chemotherapy, August 2009, p. 3211-3217, Vol. 53, No. 8
0066-4804/09/$08.00+0     doi:10.1128/AAC.00209-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Peptide-Lipid Huge Toroidal Pore, a New Antimicrobial Mechanism Mediated by a Lactococcal Bacteriocin, Lacticin Q{triangledown}

Fuminori Yoneyama,1 Yuichi Imura,3 Kanako Ohno,1 Takeshi Zendo,1 Jiro Nakayama,1 Katsumi Matsuzaki,3 and Kenji Sonomoto1,2*

Laboratory of Microbial Technology, Division of Microbial Science and Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School,1 Laboratory of Functional Food Design, Department of Functional Metabolic Design, Bio-Architecture Center, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan,2 Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-Shimo-Adachi-cho, Sakyo-ku, Kyoto 606-8501, Japan3

Received 16 February 2009/ Returned for modification 2 April 2009/ Accepted 14 May 2009

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."

* Corresponding author. Mailing address: 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. Phone and fax: (81) 92 642 3019. E-mail: sonomoto{at}agr.kyushu-u.ac.jp

{triangledown} Published ahead of print on 26 May 2009.

Antimicrobial Agents and Chemotherapy, August 2009, p. 3211-3217, Vol. 53, No. 8
0066-4804/09/$08.00+0     doi:10.1128/AAC.00209-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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