Arsenic transfer between metallothionein proteins at physiological pH

Abstract

As³+ bound to the two-domain, recombinant human metallothionein (isoform 1a) is stable at pH 7 and translocates via protein-protein interactions to other metallothionein proteins. The data show As³+ transfer from the two-domain β-α-hMT to binding sites in the isolated apo-β-hMT and apo-α-hMT. Under conditions of equilibrium, apo- and partially-metallated species coexist indicating that noncooperative demetallation of the As(6)-βα-hMT occurrs. As³+ transfer under conditions (pH 7) where the free As³+ ion is not stable, provides evidence that Cd²+ and Zn²+ transfer may also take place through protein-protein interactions and that partially metallated Cd-MT and Zn-MT would be stable.