Lantibiotic and non-lantibiotic bacteriocins are synthesised as precursor peptides containing N-terminal extensions (leader peptides) which are cleaved off during maturation. Most non-lantibiotics and also some lantibiotics have leader peptides of the so-called double-glycine type. These leader peptides share consensus sequences and also a common processing site with two conserved glycine residues in positions -1 and -2. The double- glycine-type leader peptides are unrelated to the N-terminal signal sequences which direct proteins across the cytoplasmic membrane via the sec pathway. Their processing sites are also different from typical signal peptidase cleavage sites, suggesting that a different processing enzyme is involved. Peptide bacteriocins are exported across the cytoplasmic membrane by a dedicated ATP-binding cassette (ABC) transporter. The ABC transporter is the maturation protease and its proteolytic domain resides in the N-terminal part of the protein [1]. This peptidase domain is found in a wide range of ABC transporters, however the presumed catalytic cysteine and histidine are not conserved in all members of this family.

1: Evolutionary families of metallopeptidases. Rawlings ND, Barrett AJ; Meth Enzymol 1995;248:183-228. PMID:7674922

2: A family of bacteriocin ABC transporters carry out proteolytic processing of their substrates concomitant with export. Havarstein LS, Diep DB, Nes IF; Mol Microbiol 1995;16:229-240. PMID:7565085