Biostructural analysis of the metal-sensor domain of CnrX from Cupriavidus metallidurans CH34
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In Cupriavidus metallidurans CH34, the proteins CnrX, CnrY, and CnrH regulate the expression of the cnrCBA operon that codes for a cation-efflux pump involved in cobalt and nickel resistance. The periplasmic part of CnrX can be defined as the metal sensor in the signal transduction complex composed of the membrane-bound anti-sigma factor CnrY and the extra-cytoplasmic function sigma factor CnrH. A soluble form of CnrX was overproduced and purified. This protein behaves as a dimer in solution as judged from gel filtration, sedimentation velocity experiments, and NMR. Native crystals diffracting to 2.3 Å using synchrotron radiation were obtained using the hanging-drop vapor-diffusion method. They belong to the primitive monoclinic space group P21, with unit cell parameters a = 31.87, b = 74.80, c = 93.67 Å, β = 90.107°. NMR data and secondary structure prediction suggest that this protein is essentially formed by helices.
KeywordsCnrX Cupriavidus metallidurans CH34 Extra-cytoplamic-function Heavy metal Signal transduction Structure
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