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Regulation of immunity to the two‐component lantibiotic, lacticin 3147, by the transcriptional repressor LtnR
Author(s) -
McAuliffe Olivia,
O'Keeffe Triona,
Hill Colin,
Ross R. Paul
Publication year - 2001
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2001.02290.x
Subject(s) - operon , biology , lantibiotics , repressor , gene , lactococcus lactis , genetics , structural gene , mutant , gene cluster , regulator gene , promoter , regulation of gene expression , gene expression , bacteriocin , bacteria , lactic acid
Lacticin 3147 is a membrane‐active, two‐component lantibiotic produced by Lactococcus lactis ssp. lactis DPC3147. In this study, the promoters of the lacticin 3147 gene cluster were mapped to the intergenic region between ltnR and ltnA 1 (the genes encoding the regulatory protein LtnR and the first structural gene, LtnA1), and Northern analyses revealed that the biosynthetic and immunity genes are divergently transcribed in two operons, ltnA 1 A 2 M 1 TM 2 D and ltnRIFE respectively. Although the promoter controlling biosynthesis (P bac ) appears to be constitutive, characterization of a downstream β‐galactosidase (β‐gal) fusion beyond an intragenic stem–loop structure in ltnM 1 confirmed that this putative transcriptional attenuator allows limited readthrough to the downstream biosynthetic genes, thus maintaining the correct stoichiometry between structural peptides and biosynthetic machinery. The promoter of the ltnRIFE operon (P imm ) was shown to be regulated by the transcriptional repressor LtnR. A mutant with a truncated ltnR gene exhibited a hyperimmune phenotype, whereas overexpression of ltnR resulted in cells with increased sensitivity to lacticin 3147. Gel mobility shift analysis indicated that LtnR binds to the P imm promoter region, and fusion of this promoter to the β‐gal gene of pAK80 revealed that expression from P imm is significantly reduced in the presence of LtnR. Thus, we have demonstrated that lacticin 3147 uses a regulatory mechanism not previously identified in lantibiotic systems.