title: Amino-terminal amino acids modulate sigma-factor DNA-binding activity.
abstract: Prokaryotic transcription initiation factor sigma is required for sequence-specific promoter recognition by RNA polymerase. Genetic studies have indicated that sigma itself interacts with DNA at the -10 and -35 promoter consensus sequences. Binding of Escherichia coli sigma 70 to DNA in vitro, however, can only be observed for truncated polypeptides lacking the amino-terminal amino acids. We have investigated the role of the amino terminus of E. coli sigma 70 in controlling DNA-binding ability. Deletion analysis indicates that amino acids within amino-terminal region 1.1 of sigma 70 inhibit DNA binding by the carboxy-terminal DNA-binding domains. Furthermore, inhibition of binding by the amino-terminal inhibitory domain of sigma 70 can be observed in trans. Likewise, the amino-terminal extensions of two alternative sigma-factors, E. coli sigma 32 and Bacillus subtilis sigma K, negatively affect the DNA binding activity of their carboxy-terminal domains. We propose that initiation of transcription is subject to modulation as a result of the composition and/or structure of the amino terminus of the sigma-subunit and that the sigma family of proteins belong to a larger class of intramolecularly regulated transcriptional effectors.
authors.affiliation: Department of Bacteriology, University of Wisconsin, Madison 53706.
authors.forename: A J
authors.initials: AJ
authors.lastname: Dombroski
authors.forename: W A
authors.initials: WA
authors.lastname: Walter
authors.forename: C A
authors.initials: CA
authors.lastname: Gross
mesh_terms: D000596:Amino Acids / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012808:Sigma Factor / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012808:Sigma Factor; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases