1.C.93 The Lacticin Q (Lacticin Q) Family
Lacticin Q is a peptide-lipid huge toroidal pore-forming bacteriocin produced by Lactococcus lactis QU 5 with antimicrobial activity in the nanomolar range. Lacticin Q induced calcein leakage from negatively charged liposomes. Concomitantly with calcein leakage, lacticin Q translocates from the outer to the inner leaflet of the liposomes within two seconds after initially binding to membrane. Lacticin Q also induced lipid flip-flop. Yoneyama et al., 2009 provided the first evidence for a bacteriocin from Gram-positive bacteria forming a toroidal pore. From liposomes, lacticin Q leaked fluorescence-labeled dextran with a diameter of 4.6 nm and caused leakage of small size proteins such as green fluorescence protein from live bacterial cells. The proposed pore formation model of lacticin Q is as follows: (i) quick binding to outer membrane leaflets; (ii) formation of at least 4.6 nm pores, causing protein leakage with lipid flip-flop, and (iii) migration of lacticin Q molecules from the outer to the inner membrane leaflet.