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Biochemistry. 1993 Oct 19;32(41):11112-7.

In vitro functional characterization of overproduced Escherichia coli katF/rpoS gene product.

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McArdle Laboratory for Cancer Research, University of Wisconsin-Madison 53706.


The katF/rpoS gene product (sigma s), a central regulator of stationary-phase gene expression in Escherichia coli, has been purified from an overproducing strain. sigma s was used as an immunogen for the production of monoclonal antibodies. Previous sequence analysis of sigma s strongly indicated homology to the sigma factor family. We show biochemically in this paper that sigma s is a sigma factor. This protein can bind to core RNA polymerase (E), and this binding can be competed effectively by the major E. coli transcription initiation factor, sigma 70. Immunopurified sigma s holoenzyme (E sigma s) transcribes the promoters of the bolAp1 gene and the xthA gene. Interestingly, both promoters can also be transcribed by sigma 70 holoenzyme (E sigma 70).

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