PMID: 7024271Oct 10, 1981Paper

Free sigma factor of Escherichia coli RNA polymerase can bind to DNA.

The Journal of Biological Chemistry
T Kudo, R H Doi

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.

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