Amino acid substitutions in the -35 recognition motif of sigma 70 that result in defects in phage lambda repressor-stimulated transcription.
The phage lambda repressor activates transcription of its own gene from the promoter PRM. Previous work has suggested that this activation involves a protein-protein interaction between DNA-bound repressor and RNA polymerase. To identify the subunit of RNA polymerase that participates in this putative interaction, we searched for polymerase mutants that responded poorly to repressor. We report here the isolation of three sigma mutants that caused defects in repressor-stimulated, but not basal, transcription from PRM. These mutants bear amino acid substitutions in a putative helix-turn-helix motif that sigma uses to recognize the promoter -35 region. We suggest that lambda repressor interacts directly with this helix-turn-helix motif in facilitating the formation of a productive initiating complex.
Kuldell
N
N
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115.
Hochschild
A
A
D000595:Amino Acid Sequence; D010582:Bacteriophage lambda / Q000235:genetics*; D001483:Base Sequence; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D008957:Models, Genetic; D008961:Models, Structural; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012097:Repressor Proteins / Q000235:genetics*; D012641:Selection, Genetic; D012808:Sigma Factor / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D012321:DNA-Directed RNA Polymerases; D001616:beta-Galactosidase