The lumenal loop Met 672-Pro 707 of copper-transporting ATPase ATP7A binds metals and facilitates copper release from the intramembrane sites

Amanda N. Barry, Adenike Otoikhian, Sujata Bhatt, Ujwal Shinde, Ruslan Tsivkovskii, Ninian J. Blackburn, Svetlana Lutsenko

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

The copper-transporting ATPase ATP7A has an essential role in human physiology. ATP7A transfers the copper cofactor to metalloenzymes within the secretory pathway; inactivation of ATP7A results in an untreatable neurodegenerative disorder, Menkes disease. Presently, the mechanism of ATP7A-mediated copper release into the secretory pathway is not understood. We demonstrate that the characteristic His/Met-rich segment Met 672- Pro 707 (HM-loop) that connects the first two transmembrane segments of ATP7A is important for copper release. Mutations within this loop do not prevent the ability of ATP7A to form a phosphorylated intermediate during ATP hydrolysis but inhibit subsequent dephosphorylation, a step associated with copper release. The HM-loop inserted into a scaffold protein forms two structurally distinct binding sites and coordinates copper in a mixed His-Met environment with an ∼2:1 stoichiometry. Binding of either copper or silver, a Cu(I) analog, induces structural changes in the loop. Mutations of 4 Met residues to Ile or two His-His pairs to Ala-Gly decrease affinity for copper. Altogether, the data suggest a two-step process, where copper released from the transport sites binds to the first His-(Met)2 site, triggering a structural change and binding to a second 2-coordinate His-His or His-Met site. We also show that copper binding within the HM-loop stabilizes Cu(I) and protects it from oxidation, which may further aid the transfer of copper from ATP7A to acceptor proteins. The mechanism of copper entry into the secretory pathway is discussed.

Original languageEnglish (US)
Pages (from-to)26585-26594
Number of pages10
JournalJournal of Biological Chemistry
Volume286
Issue number30
DOIs
StatePublished - Jul 29 2011

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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