IDENTIFICATION OF THE DNA-BINDING SITES FOR 2 RESPONSE REGULATORS INVOLVED IN CONTROL OF BACTERIOCIN SYNTHESIS IN LACTOBACILLUS-PLANTARUM C-11

In Lactobacillus plantarum C11, bacteriocin production has previously been shown to be an inducible process, in which a secreted peptide, pr oduced by the host itself, is involved. The inducing factor, designate d plantaricin A (PlnA), is a bacteriocin-like peptide encoded by a gen e (plnA) located on the same operon as the genes for a two-component r egulatory system (pln-BCD). This system consists of a histidine kinase (PlnB) and two response regulators (PlnC,D), and belongs to a recentl y defined subfamily of two-component regulatory systems, which are act ivated by secreted peptide pheromones through a quorum-sensing mechani sm. We show here that the two response regulators PlnC and PlnD bind s pecifically to imperfect direct repeats found within the adjacent prom oter of the plnABCD operon, and to similar sequences found within the promoter regions of two nearby operons containing bacteriocin structur al genes (plnEFI and plnJKLR). Binding of PlnC and PlnD was increased two to three fold in the presence of acetyl phosphate. The results sug gest that bacteriocin synthesis in L. plantarum C11 is regulated by th e DNA-binding activity of the two response regulators PlnC and PlnD.