Excess copper is toxic to prokaryotic cells. To guard against this potential toxicity, metalloregulatory proteins have evolved to control intracellular copper levels and prevent cellular damage. CsoR is one of the most widely distributed copper sensing metalloregulatory protein in bacteria. Homotetrameric CsoRs repress the transcription of a Cu(I)-effluxing ATPase and chaperone in its apo form. Cu(I) binding results in derepression of the gene encoding chaperone and the exporter. NMR studies of CsoR in Geobacillus thermodenitrificans (GtCsoR) (48 kD) show large chemical shift perturbations in N-terminal flexible tail and C-terminus of a2-helix upon Cu(I) binding and TALOS+ analysis shows that Cu(I) binding induces an kink in the a2-helix between two copper binding residues H75 and C79. Additionally, small angle X-ray scattering (SAXS) experiments have been performed on the wild type CsoR as well as a mutant protein involving second shell hydrogen bonding residues, Y49F/E95Q CsoR. These data reveal a detectable conformational change when Cu(I) binds to WT CsoR, while little change is observed for the Y49F/E95Q mutant protein upon Cu(I) binding. Similar conformational changes induced in the tetramer by Cu(I) were also characterized in the related CsoR from B. subtilis. Further biophysical studies are underway to elucidate how GtCsoR links Cu(I) binding to negative allosteric regulation of DNA operator binding. Supported by NIH grant GM042569 to D.P.G.

Cu(I)-mediated structural transition of Cu(I)-sensing repressor <i>Gt</i>CsoR by SAXS and NMR spectroscopy

246th National Meeting (2013)

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Cu(I)-mediated structural transition of Cu(I)-sensing repressor GtCsoR by SAXS and NMR spectroscopy