Molecular Basis of the Cooperative Binding of Cu(I) and Cu(II) to the CopK Protein from Cupriavidus metallidurans CH34
Details
Publication Year 2011-11-01, Volume 50, Issue #43, Page 9237-9247
Journal Title
BIOCHEMISTRY
Publication Type
Journal Article
Abstract
The bacterium Cupriavidus metallidurans CH34 is resistant to high environmental concentrations of many metal ions. Upon copper challenge, it upregulates the periplasmic protein CopK (8.3 kDa). The function of CopK in the copper resistance response is ill-defined, but CopK demonstrates an intriguing cooperativity: occupation of a high-affinity Cu-I binding site generates a high-affinity Cu-II binding site, and the high-affinity Cu-II binding enhances Cu-I binding. Native CopK and targeted variants were examined by chromatographic, spectroscopic, and X-ray crystallographic probes. Structures of two distinct forms of (CuCuII)-Cu-I-CopK were defined, and structural changes associated with occupation of the Cu-II site were demonstrated. In solution, monomeric (CuCuII)-Cu-I-CopK features the previously elucidated Cu-I site in Cu-I-CopK, formed from four S-delta atoms of Met28, -38, -44, and -54 (site 4S). Binding of Cu-I to apo-CopK induces a conformational change that releases the C-terminal beta-strand from the beta-sandwich structure. In turn, this allows His70 and N-terminal residues to form a large loop that includes the Cu-II binding site. In crystals, a polymeric form of (CuCuII)-Cu-I-CopK displays a Cu-I site defined by the S-delta atoms of Met26, -38, and -54 (site 3S) and an exogenous ligand (modeled as H2O) and a Cu-II site that bridges dimeric CopK molecules. The 3S Cu-I binding mode observed in crystals was demonstrated in solution in protein variant M44L where site 4S is disabled. The intriguing copper binding chemistry of CopK provides molecular insight into Cu-I transfer processes. The adaptable nature of the Cu-I coordination sphere in methionine-rich clusters allows copper to be relayed between clusters during transport across membranes in molecular pumps such as CusA and Ctrl.
Publisher
AMER CHEMICAL SOC
Keywords
COPPER TRANSPORTER; CRYSTAL-STRUCTURES; NMR-SPECTROSCOPY; MODEL; PROGRAM; COORDINATION; RESISTANCE; QUALITY
Publisher's Version
https://doi.org/10.1021/bi200841f
Rights Notice
Refer to copyright notice on published article.


Creation Date: 2011-11-01 12:00:00
Last Modified: 0001-01-01 12:00:00
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