Lantibiotics are heavily-modified bacteriocin-like peptides from Gram-positive bacteria. They contain alpha,beta-unsaturated amino acids(dehydroalanine and dehydrobutyrine) and lanthionine or 3-methyllanthioninerings (collectively known as thioether rings). There are 2 types oflantibiotic: type A (which include nisin, subtilin, epidermin, galliderminand Pep5) are strongly cationic and bactericidal - nisin, subtilin and Pep5inhibit the growth of Gram-positive bacteria, probably by voltage-dependentpore formation in the cytoplasmic membrane, resulting in cellular efflux ofelectrolytes, amino acids and ATP; type B lantibiotics possess at most onepositive charge and are not bactericidal. Nisin, subtilin, epidermin andgallidermin are believed to have evolved from a common ancestor [<cite idref="PUB00002470"/>].The sequences of lantibiotics do not adopt regular secondary structures (i.e., alpha-helices and beta-strands) because of their constituentthioether rings (5 are found in nisin). Nevertheless, the rings may beimportant in providing rigid local structures, which could be essentialfor pore formation in membranes [<cite idref="PUB00002749"/>]. Solution NMR indicates nisin tohave a screw-shaped structure, which undergoes only limited change inpassing to a membrane-mimicking environment. Nisin