DOUBLE-GLYCINE-TYPE LEADER PEPTIDES DIRECT SECRETION OF BACTERIOCINS BY ABC TRANSPORTERS - COLICIN V SECRETION IN LACTOCOCCUS-LACTIS

Many non-lantibiotic bacteriocins of lactic acid bacteria are produced as precursors which have N-terminal leader peptides that share simila rities in amino acid sequence and contain a conserved processing site of two glycine residues in positions -1 and -2. A dedicated ATP-bindin g cassette (ABC) transporter is responsible for the proteolytic cleava ge of the leader peptides and subsequent translocation of the bacterio cins across the cytoplasmic membrane. To investigate the role that the se leader peptides play in the recognition of the precursor by the ABC transporters, the leader peptides of leucocin A, lactococcin A or col icin V were fused to divergicin A, a bacteriocin from Carnobacterium d ivergens that is secreted via the cell's general secretion pathway. Pr oduction of divergicin was monitored when these fusion constructs were introduced into Leuconostoc gelidum, Lactococcus lactis and Escherich ia coli, which carry the secretion apparatus for leucocin A, lactococc ins A and B, and colicin V, respectively. The different leader peptide s directed the production of divergicin in the homologous hosts. In so me cases production of divergicin was also observed when the leader pe ptides were used in heterologous hosts. For ABC-transporter-dependent secretion in E. coli the outer membrane protein TolC was required. Usi ng this strategy, colicin V was produced in L. lactis by fusing this b acteriocin behind the leader peptide of leucocin A.