Lantibiotics

Lantibiotics are a class of polycyclic peptide antibiotics that contain the characteristic thioether amino acids lanthionine or methyllanthionine, as well as the unsaturated amino acids dehydroalanine, and 2-aminoisobutyric acid. Lantibiotics are a class of polycyclic peptide antibiotics that contain the characteristic thioether amino acids lanthionine or methyllanthionine, as well as the unsaturated amino acids dehydroalanine, and 2-aminoisobutyric acid. Lanthionine is composed of two alanine residues that are crosslinked on their β-carbon atoms by a thioether (monosulfide) linkage. Lantibiotics are produced by a large number of Gram-positive bacteria such as Streptococcus and Streptomyces to attack other Gram-positive bacteria, and as such, they are considered a member of the bacteriocins. Bacteriocins are classified according to their extent of posttranslational modification. The lantibiotics are a class of more extensively modified bacteriocins, also called Class I bacteriocins. (Bacteriocins for which disulfide bonds are the only modification to the peptide are Class II bacteriocins.) Lantibiotics are well studied because of the commercial use of these bacteria in the food industry for making dairy products such as cheese. Nisin and epidermin are members of a family of lantibiotics that bind to lipid II, a cell wall precursor lipid component of target bacteria and disrupt cell wall production. The duramycin family of lantibiotics binds phosphoethanolamine in the membranes of its target cells and seem to disrupt several physiological functions. The name lantibiotics was introduced in 1988 as an abbreviation for 'lanthionine-containing peptide antibiotics'. The first structures of these antimicrobial agents were produced by pioneering work by Gross and Morell in the late 1960s and early 1970s, thus marking the formal introduction of lantibiotics. Since then, lantibiotics such as nisin have been used auspiciously for food preservation and have yet to encounter significant bacterial resistance. These attributes of lantibiotics have led to more detailed research into their structures and biosynthetic pathways. Some contain 2 peptides, e.g. haloduracin. (Sublancin may be an S-linked glycopeptide. They are synthesised with a leader polypeptide sequence that is removed only during the transport of the molecule out of the synthesising cell. They are synthesized by ribosomes, which distinguishes them from most natural antibiotics. There are four known enzymes (lanthipeptide synthetases) responsible for producing lanthionine rings.