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Conserved residues modulate copper release in human copper chaperone Atox1.

Authors
  • Hussain, Faiza
  • Olson, John S
  • Wittung-Stafshede, Pernilla
Type
Published Article
Journal
Proceedings of the National Academy of Sciences
Publisher
Proceedings of the National Academy of Sciences
Publication Date
Aug 12, 2008
Volume
105
Issue
32
Pages
11158–11163
Identifiers
DOI: 10.1073/pnas.0802928105
PMID: 18685091
Source
Medline
License
Unknown

Abstract

It is unclear how the human copper (Cu) chaperone Atox1 delivers Cu to metal-binding domains of Wilson and Menkes disease proteins in the cytoplasm. To begin to address this problem, we have characterized Cu(I) release from wild-type Atox1 and two point mutants (Met(10)Ala and Lys(60)Ala). The dynamics of Cu(I) displacement from holo-Atox1 were measured by using the Cu(I) chelator bicinchonic acid (BCA) as a metal acceptor. BCA removes Cu(I) from Atox1 in a three-step process involving the bimolecular formation of an initial Atox1-Cu-BCA complex followed by dissociation of Atox1 and the binding of a second BCA to generate apo-Atox1 and Cu-BCA(2). Both mutants lose Cu(I) more readily than wild-type Atox1 because of more rapid and facile displacement of the protein from the Atox1-Cu-BCA intermediate by the second BCA. Remarkably, Cu(I) uptake from solution by BCA is much slower than the transfer from holo-Atox1, presumably because of slow dissociation of DTT-Cu complexes. These results suggest that Cu chaperones play a key role in making Cu(I) rapidly accessible to substrates and that the activated protein-metal-chelator complex may kinetically mimic the ternary chaperone-metal-target complex involved in Cu(I) transfer in vivo.

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