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

Zhou, Liang, Singleton, Chloe and Le Brun, Nick E. ORCID: https://orcid.org/0000-0001-9780-4061 (2008) High Cu(I) and low proton affinities of the CXXC motif of Bacillus subtilis CopZ. Biochemical Journal, 413 (3). 459–465. 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
Depositing User: Rachel Smith
Date Deposited: 07 Apr 2011 14:16
Last Modified: 11 Jan 2023 17:33
URI: https://ueaeprints.uea.ac.uk/id/eprint/28488
DOI: 10.1042/BJ20080467

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