High Cu(I) and low proton affinities of the CXXC motif of Bacillus subtilis CopZ

Zhou, Liang, Singleton, Chloe and Le Brun, Nick E. (2008) High Cu(I) and low proton affinities of the CXXC motif of Bacillus subtilis CopZ. Biochemical Journal, 413 (3). p. 459. ISSN 0264-6021

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Abstract

CopZ, an Atx1-like copper chaperone from the bacterium Bacillus subtilis, functions as part of a complex cellular machinery for Cu(I) trafficking and detoxification, in which it interacts specifically with the transmembrane Cu(I)-transporter CopA. Here we demonstrate that the cysteine residues of the MXCXXC Cu(I)-binding motif of CopZ have low proton affinities, with both exhibiting pKa values of 6 or below. Chelator competition experiments demonstrated that the protein binds Cu(I) with extremely high affinity, with a small but significant pH-dependence over the range pH 6.5–8.0. From these data, a pH-corrected formation constant, ß2=~6×1022 M-2, was determined. Rapid exchange of Cu(I) between CopZ and the Cu(I)-chelator BCS (bathocuproine disulfonate) indicated that the mechanism of exchange does not involve simple dissociation of Cu(I) from CopZ (or BCS), but instead proceeds via the formation of a transient Cu(I)-mediated protein–chelator complex. Such a mechanism has similarities to the Cu(I)-exchange pathway that occurs between components of copper-trafficking pathways.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Related URLs:
Depositing User: Rachel Smith
Date Deposited: 07 Apr 2011 14:16
Last Modified: 21 Apr 2020 19:12
URI: https://ueaeprints.uea.ac.uk/id/eprint/28488
DOI: 10.1042/BJ20080467

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