Binding properties and stoichiometries of a palladium(II) complex to metallothioneins in vivo and in vitro.

This paper will be the first to discuss the in vivo and in vitro properties of a Pd(II) complex, K2PdCl4, interacting with metallothioneins (MTs). In vivo experiments revealed that intraperitoneal injections of K2PdCl4 into rabbits led to the simultaneous synthesis of Pd-MT in the kidney and Zn7MT in the liver. The renal Pd-MT complex contains 3.6 +/- 0.3 Pd, 2.1 +/- 0.2 Zn, and 1.0 +/- 0.1 Cu per mole protein. It was found that pre-treatment with Zn(NO3)2 before K2PdCl4 injections significantly enhanced renal Pd-MT level. The same pre-treatment also increases hepatic Zn-MT levels. These results strongly suggest that Pd(II) ions can be bound in vivo by MT existing in the rabbit kidneys to form Pd-MT. Gel-filtration chromatographic studies after the incubation of either native Cd5Zn2MT2 or Zn7MT2 with K2PdCl4 in vitro demonstrate that Pd(II) ions promote the non-oxidative oligomerization of native MTs. Increasing the level of Pd(II) relative to MT led to a concomitant increase in the apparent yield of MT oligomers. At relatively low Pd-MT ratio, Pd(II) is found predominantly in the oligomers while the monomeric products are chiefly composed of the reactants, Cd5Zn2MT2 or Zn7MT2. Based on our experimental data, the mechanisms of the reactions between Pd(II) and MTs in vivo and in vitro are discussed.