Lanthionines are thioether bridges that are putatively generated by dehydration of Ser and Thr residues followed by addition of cysteine residues within the peptide. This family contains the lanthionine synthetase C-like proteins 1 and 2 which are related to the bacterial lanthionine synthetase components C (LanC). LANCL1 (P40 seven-transmembrane-domain protein) and LANCL2 (testes-specific adriamycin sensitivity protein) are thought to be peptide-modifying enzyme components in eukaryotic cells. Both proteins are produced in large quantities in the brain and testes and may have role in the immune surveillance of these organs. Lanthionines are found in lantibiotics, which are peptide-derived, post-translationally modified antimicrobials produced by several bacterial strains. This region contains seven internal repeats.