Mechanistic studies of lantibiotic-induced permeabilization of phospholipid vesicles

Abstract

Nisin is a cationic polycyclic bacteriocin secreted by some lactic acid bacteria. Nisin has previously been shown to permeabilize liposomes. The interaction of nisin was analyzed with liposomes prepared of the zwitterionic phosphatidylcholine (PC) and the anionic phosphatidylglycerol (PG). Nisin induces the release of 6-carboxyfluorescein and other small anionic fluorescent dyes from PC liposomes in a delta psi-stimulated manner, and not that of neutral and cationic fluorescent dyes. This activity is blocked in PG liposomes. Nisin, however, efficiently dissipates the delta psi in cytochrome c oxidase proteoliposomes reconstituted with PG, with a threshold delta psi requirement of about -100 mV. Nisin associates with the anionic surface of PG liposomes and disturbs the lipid dynamics near the phospholipid polar head group-water interface. Further studies with a novel cationic lantibiotic, epilancin K7, indicate that this molecule penetrates into the hydrophobic carbon region of the lipid bilayer upon the imposition of a delta psi. It is concluded that nisin acts as an anion-selective carrier in the absence of anionic phospholipids. In vivo, however, this activity is likely to be prevented by electrostatic interactions with anionic lipids of the target membrane. It is suggested that pore formation by cationic (type A) lantibiotics involves the local perturbation of the bilayer structure and a delta psi-dependent reorientation of these molecules from a surface-bound into a membrane-inserted configuration.

Structure‐activity relationships in the peptide antibiotic nisin: antibacterial activity of fragments of nisin

“…Earlier evidence has shown that this is also true for ring k; acid hydrolysis at Dha 5 in nisin ~ a2 amide leads to loss of tctivity [13], but the Dha5Ala mutant retains full antibacterial tctivity [12], showing that it is the intact ring A, rather than he dehydro residue at position 5, which is required for this tctivity. The 'wedge' model for the formation by nisin of transient pores in the bacterial membrane by induction of non-bilayer structures [10,26] postulates that the N-terminal part of nisin, comprising rings A-C, is responsible for binding of nisin to the membrane surface and/or its oligomerisation, while the more cationic C-terminal part of the molecule plays a role in pore formation. The present evidence is consistent with the idea that intact rings A and C are required for this binding function, and suggests that some pore formation is possible in the absence of the cationic C-terminal segment.…”

“…The simplest explanation of the effects of nisin 1-12 is that it competes with nisin for some site which is essential for pore formation. The observation that nisin is able to form pores in protein-free liposomes [26] makes it unlikely that this essential site is a protein, but two other possibilities remain. First, nisin 1-12 could compete for a site on the cell membrane to which nisin must bind as a preliminary to pore formation -probably phosphatidyl glycerol [10,26].…”

“…The observation that nisin is able to form pores in protein-free liposomes [26] makes it unlikely that this essential site is a protein, but two other possibilities remain. First, nisin 1-12 could compete for a site on the cell membrane to which nisin must bind as a preliminary to pore formation -probably phosphatidyl glycerol [10,26]. Secondly, the competition could be at the level of the oligomerisation of nisin required for pore formation, if one postulates that an oligomer containing some nisin and some nisin 1-12 molecules is inactive.…”

Structure and Biological Activity of Chemically Modified Nisin A Species

“…The exact molecular mechanism of the growth-inhibiting effect of nisin is still not fully understood, although several studies have found indications that nisin interacts with the bacterial cell membrane forming pores ultimately leading to cell lysis (Hurst, 1981 ;Gao et al, 1991 ;Driessen et a]., 1995;Sahl et al, 1995).…”

Surface Location and Orientation of the Lantibiotic Nisin Bound to Membrane‐Mimicking Micelles of Dodecylphosphocholine and of Sodium Dodecylsulphate

“…For intact cells the threshold potential is between -50 mV and -80 mV at pH 7.5 and below -50 mV at pH 5.5 (Sahl et al, 1987). In vitro studies have indicated that the activity of nisin is highly dependent on the phospholipid composition (Gao et al, 1991 ;Garcia Garceri et al, 1993;Driessen et al, 1995).…”