THE COMPLEXATION OF METALLOTHIONEIN WITH CADMIUM ION AND ITS CONFORMATIONAL STUDY

The circular dichroic (CD) spectra of native mouse liver MT-2 (pH 6.10) and re-constituted MT (pH adjusted from 6.10 to 1.84, and then raised to 10.70) have been measured to determine if there are any conformational differences between them. The pH value corresponding to the complete dissociation of Cd2+ from rabbit MT-1 is 2.8. Compared with the data derived from a cadmium-selective electrode, the CD spectra of native rabbit liver MT-1 at different pH values (8.19, 4.44, 3.61, 2.94 and 1.92) demonstrate that the release of the metal ions with accompanied by a conformational change in the MT and that the metalthiolate bond is important in maintaining the secondary structure of MT. At pH 8.19 the addition of excess Cd2+ results in a significant change in the CD spectrum of rabbit MT-1, indicating that some metal clusters have been broken.