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J. Bacteriol., 06 1995, 3546-3555, Vol 177, No. 12
TJ Goss and RA Bender
A 32-kDa polypeptide corresponding to NAC, the product of the Klebsiella
aerogenes nac gene, was overexpressed from a plasmid carrying a tac'-'nac
operon fusion and purified to near homogeneity by taking advantage of its
unusual solubility properties. NAC was able to shift the electrophoretic
migration of DNA fragments carrying the NAC- sensitive promoters hutUp,
putPp1, and ureDp. The interaction between NAC and hutUp was localized to a
26-bp region centered approximately 64 bp upstream of the hutUp
transcription initiation site. Moreover, NAC protected this region from
DNase I digestion. Mobility shift and DNase I protection studies utilizing
the putP and ureD promoter regions identified NAC-binding regions of sizes
and locations similar to those found in hutUp. Comparison of the DNA
sequences which were protected from DNase I digestion by NAC suggests a
minimal NAC-binding consensus sequence: 5'-ATA-N9-TAT-3'. In vitro
transcription assays demonstrated that NAC was capable of activating the
transcription of hutUp by sigma 70-RNA polymerase holoenzyme when this
promoter was presented as either a linear or supercoiled DNA molecule.
Thus, NAC displays the in vitro DNA-binding and transcription activation
properties which have been predicted for the product of the nac gene.
Copyright © 1995, American Society for Microbiology
The nitrogen assimilation control protein, NAC, is a DNA binding transcription activator in Klebsiella aerogenes
Department of Biology, University of Michigan, Ann-Arbor 48109-1048, USA.
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