STRUCTURAL STUDIES ON METAL SERUM-ALBUMIN - III - SLOW CONFORMATIONALTRANSITION OF HSA AND BSA INDUCED BY NI2+ ION

A notable hysteretic effect has been observed in the interaction of Ni 2+ ion with human or bovine serum albumin using UV-Visible spectrometr y, which shows that the binding of Ni2+ ion can induce a slow transiti on of HSA and BSA from the conformation of weaker affinity for Ni2+ io n to the one of stronger affinity (T - R transition). This conformatio nal transition is supported by the time dependence of the optical rota tion of the samples. The rate constants and activation parameters of t hese transitions have been measured and discussed. It is inferred that such a conformational transition may mainly occur in the IA subdomain of the proteins,and is likely to be a ''hinged movement'',which makes the IA subdomain become more open.