Reactions of cisplatin (cis-[

No abstract

We report one-dimensional and two-dimensional 1H-NMR studies of the binding of Ni2+, Cu2+, Co2+, Cd2+ and Al3+ to defatted bovine and human serum albumins. The diamagnetic shifts induced by Ni2+, and paramagnetic effects due to Cu2+, were consistent with strong binding to a square-planar site formed by the three N-terminal amino acid residues (Asp-Thr-His for bovine, and Asp-Ala-His for human albumin). In contrast to previous studies on isolated 1-24 N-terminal peptide, a Lys residue also appeared to be involved in the binding site, and is assigned as Lys4. A second His residue is also close to the Cu2+/Ni2+ binding site in bovine serum albumin and is assigned to His59 (not present in human albumin). Co2+ caused specific perturbation of the resonances for the three N-terminal residues as well as those for Lys4. This is the first evidence for Co2+ binding to the N-terminal metal site of serum albumin. Neither Al3+ nor Cd2+ perturbed resonances for the N-terminal amino acids, but bind elsewhere in the protein.

) -EJB 94 0702/3 1. Reactions of fatty-acid-free bovine serum albumin and recombinant human albumin with a range of antiarthritic gold(1) complexes [auranofin, deacetylated auranofin, triethylphosphinegold(1) chloride] and related thiols (thioglucose, tetraacetylthioglucose, glutathione, dithiothreitol) have been investigated using 'H-NMR spectroscopy.2. In reactions of albumin with auranofin, tetraacetylthioglucose and dithothreitol, release of cystine was detected, whereas for deacetylated auranofin, thioglucose and glutathione, mixed disulphides with cysteine were produced. It has been previously proposed that Cys34 of human and bovine serum albumins is partly blocked by disulphide formation with cysteine and glutathione. The above reactions lead to deblocking by thiol-disulphide interchange reactions. No release of glutathione from albumin was detected.3. Changes in the His HE^ regions of the 'H-NMR spectra show that albumin exists in two structural forms dependent on whether the side-chain of Cys34 is a free thiolate, or blocked by gold(I)triethylphosphine, by disulphide formation with cysteine or by another form of oxidation. We propose that Cys34 is either in a buried or in an exposed environment; the possible molecular basis of the structural change is discussed.4. The relationship between reactions at Cys34, cysteine release, and the observed structural transition are discussed in terms of chrysotherapy, albumin metabolism and the use of gold(1) as a heavy atom derivative in X-ray crystallographic studies of albumins.Serum albumin is the major plasma protein, accounting for about 60% of the total protein in blood serum, with a concentration of about 42 g 1-' (0.63 mM) [I]. Albumin is a single-chain protein of about 580 amino acids (66.5 kDa) containing 35 cysteine residues formed into 17 structural disulphide bonds plus one free thiolate (Cys34). The protein is composed of three structurally similar domains [2, 31, each Correspondence to P. J. Sadler,