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A plasmid-encoded two-component regulatory system involved in copper-inducible transcription in Lactococcus lactis
N Khunajakr1, C Q Liu, P Charoenchai
1Cooperative Research Centre for Food Industry Innovation, Department of Biotechnology, University of New South Wales, Sydney 2052, Australia.
Abstract:
Two regulatory genes (lcoR and lcoS) were identified from a plasmid-borne lactococcal copper resistance determinant and characterized by transcriptional fusion to the promoterless chloramphenicol acetyltransferase gene (cat). RT-PCR analysis indicates that lcoR and lcoS are organized within an operon, controlling the transcription of cat in a copper-inducible manner. The amino acid sequences deduced from lcoR and lcoS show homology to the response and sensor proteins of known two-component regulatory systems. Deletion within either lcoS or both genes inactivated the copper-dependent activity, suggesting the presence of no trans-acting lcoR and lcoS homologs in the lactococcal host chromosome. The transcription start site involved in copper induction was mapped by primer extension.