A family of bacteriocin ABC transporters carry out proteolytic processing of their substrates concomitant with export.
Lantibiotic and non-lantibiotic bacteriocins are synthesized 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. Here we show that the ABC transporter is the maturation protease and that its proteolytic domain resides in the N-terminal part of the protein. This result demonstrates that the ABC transporter has a dual function: (i) removal of the leader peptide from its substrate, and (ii) translocation of its substrate across the cytoplasmic membrane. This represents a novel strategy for secretion of bacterial proteins.
Håvarstein
L S
LS
Laboratory of Microbial Gene Technology, As, Norway.
Diep
D B
DB
Nes
I F
IF
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001430:Bacteriocins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D017124:Conserved Sequence; D004926:Escherichia coli / Q000378:metabolism; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D017354:Point Mutation; D011498:Protein Precursors / Q000096:biosynthesis / Q000235:genetics; D021382:Protein Sorting Signals / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D015533:Transcriptional Activation
D018528:ATP-Binding Cassette Transporters; D001430:Bacteriocins; C095766:LagA protein, Lactococcus lactis; D011498:Protein Precursors; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; C069325:lactococcin A