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Probing the Coordination Environment of the Human Copper Chaperone HAH1: Characterization of Hg II ‐Bridged Homodimeric Species in Solution
Author(s) -
Łuczkowski Marek,
Zeider Brian A.,
Hinz Alia V. H.,
Stachura Monika,
Chakraborty Saumen,
Hemmingsen Lars,
Huffman David L.,
Pecoraro Vincent L.
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201204184
Subject(s) - chemistry , copper , metal , crystallography , atp7a , monomer , golgi apparatus , kinetics , metal ions in aqueous solution , inorganic chemistry , atpase , biochemistry , enzyme , organic chemistry , cell , polymer , physics , quantum mechanics
Although metal ion homeostasis in cells is often mediated through metallochaperones, there are opportunities for toxic metals to be sequestered through the existing transport apparatus. Proper trafficking of Cu I in human cells is partially achieved through complexation by HAH1, the human metallochaperone responsible for copper delivery to the Wilson and Menkes ATPase located in the trans‐Golgi apparatus. In addition to binding copper, HAH1 strongly complexes Hg II , with the X‐ray structure of this complex previously described. It is important to clarify the solution behavior of these systems and, therefore, the binding of Hg II to HAH1 was probed over the pH range 7.5 to 9.4 using 199 Hg NMR, 199m Hg PAC and UV–visible spectroscopies. The metal‐dependent protein association over this pH range was examined using analytical gel‐filtration. It can be concluded that at pH 7.5, Hg II is bound to a monomeric HAH1 as a two coordinate, linear complex (HgS 2 ), like the Hg II –Atx1 X‐ray structure (PDB ID: 1CC8). At pH 9.4, Hg II promotes HAH1 association, leading to formation of HgS 3 and HgS 4 complexes, which are in exchange on the μs–ns time scale. Thus, structures that may represent central intermediates in the process of metal ion transfer, as well as their exchange kinetics have been characterized.