COMPLEXATION PROPERTIES OF THE METALLOTHIONEIN FRAGMENT LYS-CYS-THR-CYS-CYS-ALA[56-61] MT-I WITH ZINC USING SQUARE-WAVE VOLTAMMETRY

An electrochemical study of Zn complexation with the peptide Lys-Cys-T hr-Cys-Cys-Ala thionein fragment [56-61] MT I (FT) of mouse liver was performed using square wave voltammetry in order to enable comparisons between the behaviour of Cd,Zn metallothioneins with that of this les s complex molecule, intrinsic to the metallothionein structure. Optimu m instrumental parameters were used in order to get the best resolutio n of the voltammetric peaks of both free and complexed zinc; these bei ng low square wave frequencies and low square wave amplitudes. Complex ation equilibria of the Zn-FT system as a function of metal-ligand pro portion and, for a given metal-ligand ratio, as a function of pH have been studied. From the results obtained, the existence of a main compl ex with a stoichiometry of 1:1, in which the three thiolate groups are involved in the complexation reaction, is suggested. Another complex of a different structure and having different characteristics to the m ain one, probably also exists.