Mutational and functional analysis of the korA and korB gene products of Streptomyces plasmid p1J101

摘要: ThekorA andkorB loci ofStreptomyces lividans plasmid pIJ101 have previously been shown to control expression of the pIJ101tra (formerlykilA) andkilB genes at the transcriptional level. We show here that mutations in translational open reading frames (ORFs) that map within the kor loci abolish repression of theS. lividans lac gene directed by thetra andkilB promoters. Introduction of thekorA andkorB ORFs intoEscherichia coli maxicells under control of anE. coli promoter gave rise to 31 kDa and 10 kDa proteins that correspond in size to the products expected from the sequences of the respective ORFs; these proteins controlled transcription from the pIJ101tra andkilB promoters in theE. coli host. Mutations that affected the KorA or KorB phenotype altered the structure of, or eliminated, the protein products of thekorA andkorB ORFs, further demonstrating that these ORFs encode the functional repressors of …