Characterization of the copper(II)- and nickel(II)-transport site of human serum albumin. Studies of copper(II) and nickel(II) binding to peptide 1-24 of human serum albumin by 13C and 1H NMR spectroscopy.
As a basis for understanding the role of albumin in the transport of metal ions, detailed investigations have been carried out to elucidate the structure of Ni(II)- and Cu(II)-binding site of the peptide residue corresponding to the NH2-terminal peptide fragment 1-24 of human serum albumin by 1H and 13C NMR spectroscopy. These studies have been conducted in aqueous medium at different pH values and at different ligand/metal ratios. The results show the following: (i) Diamagnetic Ni(II) complex and paramagnetic Cu(II) complex are in slow exchange NMR time scale. (ii) Titration results of Ni(II)-bound form of peptide 1-24 show the presence of a 1:1 complex in the wide pH range (6.0-11.0), and the same stoichiometry is proposed for Cu(II) as well. (iii) Analysis of the spectra suggests that both Ni(II) and Cu(II) have one specific binding site at the NH2-terminal tripeptide segment (Asp-Ala-His...) involving the Asp alpha-NH2, His N(1) imidazole, two deprotonated peptide nitrogens (Ala NH and His NH), and the Asp COO- group. (iv) Complexation of Ni(II) and Cu(II) causes conformational change near the metal-binding site of the polypeptide chain, but there is no other binding group involved besides those in the first three residues.
D001665:Binding Sites; D003300:Copper / Q000097:blood*; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009532:Nickel / Q000097:blood*; D010446:Peptide Fragments / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D012709:Serum Albumin / Q000378:metabolism*; D000075462:Serum Albumin, Human
D010446:Peptide Fragments; D012709:Serum Albumin; D003300:Copper; D009532:Nickel; C042510:serum albumin (1-24); D000075462:Serum Albumin, Human