polypeptide peptide antibiotic lantibiotic A class of peptide antibiotic characterised by the presence of the rare thioether amino acids lanthionine or methyllanthionine, as well as the unsaturated amino acids dehydroalanine and 2-aminoisobutyric acid. In contrast to classical peptide antibiotics, lantibiotics are synthesised from precursor genes using the ribosomal pathway and the characteristic rare amino acids are introduced by posttranslational modification procedues into the lantibiotic precursor peptides ('prepeptides'). Lantibiotics are subdivided into two types: type A have long, flexible structures, while type B have rigid, globular structures. chebi_ontology CHEBI:71644 lantibiotics