DNA distortion mechanism for transcriptional activation by ZntR, a Zn(II)-responsive MerR homologue in Escherichia coli

J Biol Chem. 1999 Dec 31;274(53):37517-24. doi: 10.1074/jbc.274.53.37517.

Abstract

MerR-like DNA distortion mechanisms have been proposed for a variety of stress-responsive transcription factors. The Escherichia coli ZntR protein, a homologue of MerR, has recently been shown to mediate Zn(II)-responsive regulation of zntA, a gene involved in Zn(II) detoxification. To determine whether the MerR DNA distortion mechanism is conserved among MerR family members, we have purified ZntR to homogeneity and shown that it is a zinc receptor that is necessary and sufficient to stimulate Zn-responsive transcription at the zntA promoter. Biochemical, DNA footprinting, and in vitro transcription assays indicate that apo-ZntR binds in the atypical 20-base pair spacer region of the promoter and distorts the DNA in a manner that is similar to apo-MerR. The addition of Zn(II) to ZntR converts it to a transcriptional activator protein that introduces changes in the DNA conformation. These changes apparently make the promoter a better substrate for RNA polymerase. We propose that this zinc-sensing homologue of MerR restructures the target promoter in a manner similar to that of other stress-responsive transcription factors. The ZntR metalloregulatory protein is a direct Zn(II) sensor that catalyzes transcriptional activation of a zinc efflux gene, thus preventing intracellular Zn(II) from exceeding an optimal but as yet unknown concentration.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / metabolism*
  • Base Sequence
  • DNA Primers
  • DNA, Bacterial / chemistry*
  • DNA, Bacterial / metabolism
  • DNA-Binding Proteins / metabolism*
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Molecular Sequence Data
  • Recombinant Proteins / genetics
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / isolation & purification
  • Transcription Factors / metabolism*
  • Transcriptional Activation*
  • Zinc / metabolism*

Substances

  • Bacterial Proteins
  • DNA Primers
  • DNA, Bacterial
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • MerR protein, Bacteria
  • Recombinant Proteins
  • Transcription Factors
  • ZntR protein, E coli
  • ZntR protein, bacteria
  • Zinc