Structural and functional diversity of lantibiotic immunity proteins.

Lantibiotics are posttranslationally modified antimicrobial peptides produced by some Gram-positive bacteria. After secreting mature lantibiotics, producer cells are at risk for self-destruction. Lantibiotic-producing strains express immunity protein(s) to protect cells against their own products. To date, several types of immunity proteins with diverse structures and functions have been identified. These proteins consist of ABC transporters, lipoproteins, membrane-associated peptides, and transmembrane proteins. The ABC transporters for lantibiotic immunity export membrane-associated lantibiotics to the extracellular space by using ATP hydrolysis as a driving force. Lipoproteins and some membrane proteins for lantibiotic immunity interact with lantibiotics. Some lantibiotic producers equip themselves with 2 immunity systems, which function differently but work synergistically. The immunity levels conferred by lantibiotic immunity proteins are highly specific to their original lantibiotics and structurally related analogues. This review outlines structures and molecular functions of lantibiotic immunity proteins.