Equilibrium dialysis of metal-serum albumin. I. Successive stability constants of Zn(II)-serum albumin and the Zn(2+)-induced cross-linking self-association

• Published in: Biophysical chemistry Vol. 51; no. 1; pp. 81 - 87
• Main Authors: Zhou, Y, Wang, Y, Hu, X, Huang, J, Hao, Y, Liu, H, Shen, P
• Format: Journal Article
• Language: English
• Published: Netherlands 01.07.1994
• Subjects: Animals; Cattle; Humans; Kinetics; Mathematics; Models, Theoretical; Serum Albumin - metabolism; Serum Albumin, Bovine - metabolism; Zinc - metabolism
• ISSN: 0301-4622
• DOI: 10.1016/0301-4622(94)00032-8

The binding of Zn(II) to human serum albumin (HSA) and bovine serum albumin (BSA) was intensively studied by equilibrium dialysis. The successive stability constants were obtained by least-squares fitting. For both the Zn(II)-HSA and Zn(II)-BSA systems, the successive stability constants are basically similar, though such constants for the latter generally slightly larger than those for the former; the order of magnitude of K1 and K2 was found to be approximately 10(5) M-1. The twelve binding sites found for Zn(II)-HSA and fourteen binding sites for Zn(II)-BSA can be divided into three and two different sets, respectively, but in both systems, there exist approximately three identical strongest binding sites. The binding equilibrium of Zn(II)-HSA markedly depends on the concentration of HSA. The type of Scatchard plots indicates the existence of the Zn(2+)-induced cross-linking self-association of HSA, which was found from Wyman plots to be the strongest at a concentration of Zn2+ in the range (4-6) x 10(-6) M. The maximum of the apparent self-association constants k2 so obtained was approximately 2.6 x 10(4) M-1. Such a self-association mechanism and the order of magnitude of K1 and K2 both to some extent support the inference that the zinc group ions are bound to the cysteinyl sulphur atoms.