title: Thermodynamic and spectroscopic study of Cu(II) and Ni(II) binding to bovine serum albumin.
abstract: The thermodynamics of Cu(II) and Ni(II) binding to bovine serum albumin (BSA) have been studied by isothermal titration calorimetry (ITC). The Cu(II) binding affinity of the N-terminal protein site is quantitatively higher when the single free thiol, Cys-34, is reduced (mercaptalbumin), compared to when it is oxidized or derivatized with N-ethylmaleimide. This increased affinity is due predominantly to entropic factors. At higher pH (approximately 9), when the protein is in the basic (B) form, a second Cu(II) binds with high affinity to albumin with reduced Cys-34. The Cu(II) coordination has been characterized by UV-vis absorption, CD, and EPR spectroscopy, and the spectral data are consistent with thiolate coordination to a tetragonal Cu(II), indicating this is a type 2 copper site with thiolate ligation. Nickel(II) binding to the N-terminal site of BSA is also modulated by the redox/ligation state of Cys-34, with higher Ni(II) affinity for mercaptalbumin, the predominant circulating form of the protein.
authors.affiliation: Department of Chemistry, Dartmouth College, Hanover, NH 03755-3564, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Dean E
authors.initials: DE
authors.lastname: Wilcox
mesh_terms: D000818:Animals; D001665:Binding Sites; D002151:Calorimetry; D002417:Cattle; D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D009532:Nickel / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis; D013816:Thermodynamics
chemical_list: D008024:Ligands; D012710:Serum Albumin, Bovine; D003300:Copper; D009532:Nickel