title: Transport of Cu(II) from an albumin mimic peptide, GlyGlyHisGly, to histidine and penicillamine.
abstract: Cu in blood has been believed to transport into cell via albumin and some amino acids. To shed light on the Cu transport process we studied the reaction of the Cu(II)-peptide with the amino acid by absorption and CD spectra. Albumin mimic peptides GlyGly-L-HisGly (GGHG) and penta-Gly(G5) formed stable 4N coordinated Cu(II) complexes, but in the reaction with histidine (His) and penicillamine (Pes) the ternary Cu(II) complex formations were observed different by the kinetic study. Cu(II)-G5 complexes reacted with Pes to form the ternary complex Cu(H(-1)G5)(Pes(-)) which was subsequently transformed to the binary complex Cu(Pes(-))(2). In the system with GGHG the Cu(II) was also transported from GGHG to Pes, but the ternary Cu(H(-1)GGHG)(Pes(-)) complex as the intermediate was detected a trace. The ternary complex would be spontaneously transformed to Cu(Pes(-))(2) upon forming, because the rate constant of the ternary complex formation k(1+)= approximately 2M(-1)s(-1) was less than k(2+)= approximately 5 x 10(2)M(-1)s(-1) for the Cu(Pes(-))(2) formation at physiological pH. In the Cu(II)-GGHG-His system the ternary Cu(H(-1)GGHG)(His) complex was also hardly identified because the formation constant K(1) and k(1+) were very small and the equilibrium existed between Cu(H(-2)GGHG) and Cu(His)(2) and its overall equilibrium constant beta(2) for Cu(His)(2) was very small to be 1.00+/-0.05 M(-1) at pH 9.0. These results indicated that the ternary complex is formed in the Cu transport process from the albumin to the amino acid, but His imidazole nitrogen in the fourth-binding site of Cu(II) strongly resists the replacement by the incoming ligand.
authors.affiliation: National Institute of Radiological Sciences, Anagawa 4-9-1, Chiba 263-8555, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Hanaki
authors.forename: Akira
authors.initials: A
authors.lastname: Odani
mesh_terms: D000418:Albumins / Q000737:chemistry*; D001692:Biological Transport; D003300:Copper / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry*; D007700:Kinetics; D018716:Molecular Mimicry; D009842:Oligopeptides / Q000737:chemistry*; D010396:Penicillamine / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D000418:Albumins; D009842:Oligopeptides; D006639:Histidine; D003300:Copper; D010396:Penicillamine