Abstract: The present paper describes proton nuclear magnetic resonance studies on native rat liver metallothionein isoforms (MT-I and-I). The two isoforrns were isolated and purified from rat liver after induced by cadmium chloride. 1D NMR spin-decoupling and 2D-COSY techniques were employed in this study for the iden-tification of individual methyl resonances in metallothionein- I and一I. a-domain of metallothionein-I containing four cadmium ions was also prepared and studied by NMR to aid domain specific assignment of these resonsnces. MT was studied extensively at various pH, temperatures and ionic strengths on the basis of these resonances assignment. It is stable in the range of pH 5-9 and also at higher temperatures. The flexible part of MT is near Ala8, Va139.

Key words: Metallothionein, MT-Ⅱ a-domain, Protein NMR, Protein conforma-tion