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Solution structure of a cyanobacterial copper metallochaperone, ScAtx1

Overview

The Atx1 copper metallochaperone from Synechocystis PCC 6803, ScAtx1, interacts with two P(1)-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 betaalphabetabetaalpha 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., (2)J(NH) couplings in the imidazole ring of His-61 establish coordination, of N(epsilon2) to copper. His-61 is analogous to Lys-65 in eukaryotic, metallochaperones, stabilizing Cu(I)S(2) 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 complementary 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.

About this Structure

1SB6 is a Single protein structure of sequence from Synechocystis sp.. Full crystallographic information is available from OCA.

Reference

Solution structures of a cyanobacterial metallochaperone: insight into an atypical copper-binding motif., Banci L, Bertini I, Ciofi-Baffoni S, Su XC, Borrelly GP, Robinson NJ, J Biol Chem. 2004 Jun 25;279(26):27502-10. Epub 2004 Apr 8. PMID:15075318

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