Lantibiotic and non-lantibiotic bacteriocins are synthesised asprecursor peptides containing N-terminal extensions (leaderpeptides) which are cleaved off during maturation. Mostnon-lantibiotics and also some lantibiotics have leader peptidesof the so-called double-glycine type. These leader peptidesshare consensus sequences and also a common processing site withtwo conserved glycine residues in positions -1 and -2. Thedouble- glycine-type leader peptides are unrelated to theN-terminal signal sequences which direct proteins across thecytoplasmic membrane via the sec pathway. Their processing sitesare also different from typical signal peptidase cleavage sites,suggesting that a different processing enzyme is involved.Peptide bacteriocins are exported across the cytoplasmicmembrane by a dedicated ATP-binding cassette (ABC) transporter.The ABC transporter is the maturation protease and itsproteolytic domain resides in the N-terminal part of the protein[1]. Peptidase C39 family Peptidase_C39