Mutational and functional analysis of the korA and korB gene products of Streptomyces plasmid pIJ101

Mol Gen Genet. 1990 Jul;222(2-3):337-44. doi: 10.1007/BF00633838.


The korA and korB loci of Streptomyces lividans plasmid pIJ101 have previously been shown to control expression of the pIJ101 tra (formerly kilA) and kilB 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 the S. lividans lac gene directed by the tra and kilB promoters. Introduction of the korA and korB ORFs into Escherichia coli maxicells under control of an E. 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 pIJ101 tra and kilB promoters in the E. coli host. Mutations that affected the KorA or KorB phenotype altered the structure of, or eliminated, the protein products of the korA and korB ORFs, further demonstrating that these ORFs encode the functional repressors of the pIJ101 kil/kor gene system.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Escherichia coli / genetics
  • Gene Expression Regulation, Bacterial*
  • Genes, Bacterial
  • Lac Operon
  • Mutation
  • Phenotype
  • Plasmids / genetics*
  • Promoter Regions, Genetic
  • Protein Biosynthesis
  • Repressor Proteins / genetics*
  • Restriction Mapping
  • Streptomyces / genetics*
  • Transcription, Genetic


  • Bacterial Proteins
  • Repressor Proteins