ABSTRACT
Bacteriocins are antimicrobial peptides/proteins produced by bacteria. A number of bacteriocins are produced by lactic acid bacteria, and these are usually assigned to one of three classes. Class I, the lantibiotics, are a group of ribosomally synthesized peptides that undergo extensive posttranslational modification resulting in the formation of lanthionine bridges and other unusual amino acids. Class II are small, heat stable, non-lanthionine-containing, membrane-active peptides; and Class III comprises large, heat-labile proteins (1). Lacticin 3147, the subject of this chapter, is a two-peptide lantibiotic containing seven lanthionine groups in total. Lanthionines are formed when hydroxy amino acids (serine and threonine) are selectively dehydrated to form dehydroalanine (Dha) and dehydrobutyrine (Dhb), respectively (2). The resultant α,β-unsaturated residues may then undergo Michel addition reactions with the thiol group of specific cysteine residues to form the characteristic lanthionine (lan) and β-methyl-lanthionine (meLan) residues that have been shown to contribute to tolerance of high temperatures (3), oxidizing conditions (4), low pH (5), and proteolysis (6).
