title: Protein-protein and protein-DNA interactions of sigma70 region 4 involved in transcription activation by lambdacI.
abstract: The cI protein of bacteriophage lambda (lambdacI) activates transcription from promoter P(RM) through an acidic patch on the surface of its DNA-binding domain. Genetic evidence suggests that this acidic patch stimulates transcription from P(RM) through contact with the C-terminal domain (region 4) of the sigma(70) subunit of Escherichia coli RNA polymerase. Here, we identify two basic residues in region 4 of sigma(70) that are critical for lambdacI-mediated activation of transcription from P(RM). On the basis of structural modeling, we propose that one of these sigma(70) residues, K593, facilitates the interaction between lambdacI and region 4 of sigma(70) by inducing a bend in the DNA upstream of the -35 element, whereas the other, R588, interacts directly with a critical acidic residue within the activating patch of lambdacI. Residue R588 of sigma(70) has been shown to play an important role in promoter recognition; our findings suggest that the R588 side-chain has a dual function at P(RM), facilitating the interaction of region 4 with the promoter -35 element and participating directly in the protein-protein interaction with lambdacI.
authors.affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: Bryce E
authors.initials: BE
authors.lastname: Nickels
authors.forename: Simon L
authors.initials: SL
authors.lastname: Dove
authors.forename: Katsuhiko S
authors.initials: KS
authors.lastname: Murakami
authors.forename: Seth A
authors.initials: SA
authors.lastname: Darst
authors.forename: Ann
authors.initials: A
authors.lastname: Hochschild
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D010582:Bacteriophage lambda / Q000235:genetics; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008967:Molecular Biology / Q000379:methods; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013824:Thermus / Q000235:genetics; D015533:Transcriptional Activation; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases