3dsp | pdb_00003dsp
Crystal structure of apo copper resistance protein CopK
Structural highlights
FunctionCOPK_CUPMC Involved in resistance to copper. Can bind up to 2 copper ions. Has higher affinity for Cu(+) than for Cu(2+).[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe bacterium Cupriavidus metallidurans CH34 is resistant to high environmental concentrations of many metal ions, including copper. This ability arises primarily from the presence of a large plasmid pMOL30 which includes a cluster of 19 cop genes that respond to copper. One of the protein products CopK is induced at high levels and is expressed to the periplasm as a small soluble protein (8.3 kDa). Apo-CopK associates in solution to form a dimer (K(D) approximately 10(-5) M) whose structure was defined by NMR and X-ray crystallography. The individual molecules feature two antiparallel beta-sheets arranged in a sandwich-like structure and interact through C-terminal beta-strands. It binds Cu(II) with low affinity (K(D)(Cu(II)) > 10(-6) M) but Cu(I) with high affinity (K(D)(Cu(I)) = 2 x 10(-11) M). Cu(I)-CopK was also a dimer in the solid state and featured a distorted tetrahedral site Cu(I)(S-Met)(3)(NCS). The isothiocyanato ligand originated from the crystallization solution. Binding of Cu(I) or Ag(I), but not of Cu(II), favored the monomeric form in solution. While Ag(I)-CopK was stable as isolated, Cu(I)-CopK was moderately air-sensitive due to a strong binding cooperativity between Cu(I) and Cu(II). This was documented by determination of the Cu(I) and Cu(II) binding affinities in the presence of the other ion: K(D)(Cu(I)) = 2 x 10(-13) M and K(D)(Cu(II)) = 3 x 10(-12) M, that is, binding of Cu(II) increased the affinity for Cu(I) by a factor of approximately 10(2) and binding of Cu(I) increased the affinity for Cu(II) by a factor of at least 10(6). Stable forms of both Cu(I)Cu(II)-CopK and Ag(I)Cu(II)-CopK were isolated readily. Consistent with this unprecedented copper binding chemistry, NMR spectroscopy detected three distinct forms: apo-CopK, Cu(I)-CopK and Cu(I)Cu(II)-CopK that do not exchange on the NMR time scale. This information provides a valuable guide to the role of CopK in copper resistance. Unprecedented Binding Cooperativity between Cu(I) and Cu(II) in the Copper Resistance Protein CopK from Cupriavidus metallidurans CH34: Implications from Structural Studies by NMR Spectroscopy and X-Ray Crystallography.,Chong LX, Ash MR, Maher MJ, Hinds MG, Xiao Z, Wedd AG J Am Chem Soc. 2009 Feb 24. PMID:19236095[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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