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Solution structures of a cyanobacterial metallochaperone: Insight into an atypical copper-binding motif

Lookup NU author(s): Dr Gilles Borrelly, Professor Nigel Robinson

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Abstract

The Atx1 copper metallochaperone from Synechocystis PCC 6803, ScAtx1, interacts with two P1-type copper ATPases to supply copper proteins within intracellular compartments, avoiding ATPases for other metals en route. Here we report NMR-derived solution structures for ScAtx1. The monomeric apo form has a βαββα fold with backbone motions largely restricted to loop 1 containing Cys-12 and Cys-15. The tumbling rate of Cu(I)ScAtx1 (0.1-0.8 mm) implies dimers. Experimental restraints are satisfied by symmetrical dimers with Cys-12 or His-61, but not Cys-15, invading the copper site of the opposing subunit. A full sequence of copper ligands from the cell surface to thylakoid compartments is proposed, considering in vitro homodimer liganding to mimic in vivo liganding in ScAtx1-ATPase heterodimers. A monomeric high resolution structure for Cu(I)ScAtx1, with Cys-12, Cys-15, and His-61 as ligands, is calculated without violations despite the rotational correlation time. 2JNH couplings in the imidazole ring of His-61 establish coordination of Nε2 to copper. His-61 is analogous to Lys-65 in eukaryotic metallochaperones, stabilizing Cu(I)S2 complexes but by binding Cu(I) rather than compensating charge. Cys-Cys-His ligand sets are an emergent theme in some copper metallochaperones, although not in related Atx1, CopZ, or Hah1. Surface charge (Glu-13) close to the metal-binding site of ScAtx1 is likely to support interaction with complemen. tary surfaces of copper-transporting ATPases (PacS-Arg-11 and CtaA-Lys-14) but to discourage interaction with zinc ATPase ZiaA and so inhibit aberrant formation of copper-ZiaA complexes.


Publication metadata

Author(s): Banci L, Bertini I, Ciofi-Baffoni S, Su X-C, Borrelly GPM, Robinson NJ

Publication type: Article

Publication status: Published

Journal: Journal of Biological Chemistry

Year: 2004

Volume: 279

Issue: 26

Pages: 27502-27510

ISSN (print): 0021-9258

ISSN (electronic): 1083-351X

Publisher: American Society for Biochemistry and Molecular Biology, Inc.

URL: http://dx.doi.org/10.1074/jbc.M402005200

DOI: 10.1074/jbc.M402005200

PubMed id: 15075318


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