title: Free sigma factor of Escherichia coli RNA polymerase can bind to DNA.
abstract: Free sigma factor from E. coli RNA polymerase holoenzyme was shown to associate with supercoiled pBR350 and pBRH4 plasmid DNA s by two methods. The banding pattern of sigma factor through a nondenaturing polyacrylamide slab gel was significantly altered in the presence of supercoiled DNA; sigma factor had little or no affinity to linear, double- or single-stranded DNA. At saturation, approximately one sigma factor was bound/200 base pairs of supercoiled pBR350 DNA. By the nitrocellulose filter trapping method, sigma factor was able to bind supercoiled pBRH4 DNA much more efficiently than linear double-stranded pBRH4 DNA. These results suggest that sigma factor plays a role in the binding of holoenzyme to DNA and may be involved in locally denaturing DNA in the promoter region as postulated by previous investigators.
mesh_terms: D004269:DNA, Bacterial / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D010957:Plasmids; D011485:Protein Binding; D012234:Rho Factor / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D004278:DNA, Superhelical; D012234:Rho Factor; D014157:Transcription Factors; D006493:Heparin; D012321:DNA-Directed RNA Polymerases