Unification of the Copper(I) Binding Affinities of the Metallo-chaperones Atx1, Atox1, and Related Proteins DETECTION PROBES AND AFFINITY STANDARDS
AuthorXiao, Z; Brose, J; Schimo, S; Ackland, SM; La Fontaine, S; Wedd, AG
Source TitleJOURNAL OF BIOLOGICAL CHEMISTRY
PublisherAMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Document TypeJournal Article
CitationsXiao, Z., Brose, J., Schimo, S., Ackland, S. M., La Fontaine, S. & Wedd, A. G. (2011). Unification of the Copper(I) Binding Affinities of the Metallo-chaperones Atx1, Atox1, and Related Proteins DETECTION PROBES AND AFFINITY STANDARDS. JOURNAL OF BIOLOGICAL CHEMISTRY, 286 (13), pp.11047-11055. https://doi.org/10.1074/jbc.M110.213074.
Access StatusAccess this item via the Open Access location
Open Access at PMChttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC3064159
C1 - Journal Articles Refereed
Literature estimates of metal-protein affinities are widely scattered for many systems, as highlighted by the class of metallo-chaperone proteins, which includes human Atox1. The discrepancies may be attributed to unreliable detection probes and/or inconsistent affinity standards. In this study, application of the four Cu(I) ligand probes bicinchoninate, bathocuproine disulfonate, dithiothreitol (Dtt), and glutathione (GSH) is reviewed, and their Cu(I) affinities are re-estimated and unified. Excess bicinchoninate or bathocuproine disulfonate reacts with Cu(I) to yield distinct 1:2 chromatophoric complexes [Cu(I)L(2)](3-) with formation constants β(2) = 10(17.2) and 10(19.8) m(-2), respectively. These constants do not depend on proton concentration for pH ≥7.0. Consequently, they are a pair of complementary and stable probes capable of detecting free Cu(+) concentrations from 10(-12) to 10(-19) m. Dtt binds Cu(I) with K(D) ∼10(-15) m at pH 7, but it is air-sensitive, and its Cu(I) affinity varies with pH. The Cu(I) binding properties of Atox1 and related proteins (including the fifth and sixth domains at the N terminus of the Wilson protein ATP7B) were assessed with these probes. The results demonstrate the following: (i) their use permits the stoichiometry of high affinity Cu(I) binding and the individual quantitative affinities (K(D) values) to be determined reliably via noncompetitive and competitive reactions, respectively; (ii) the scattered literature values are unified by using reliable probes on a unified scale; and (iii) Atox1-type proteins bind Cu(I) with sub-femtomolar affinities, consistent with tight control of labile Cu(+) concentrations in living cells.
KeywordsBioinorganic Chemistry; Expanding Knowledge in the Chemical Sciences
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