Transcriptional activation of the rainbow trout metallothionein-A gene by Zn and Ag

摘要: Metallothionein (MT) is a low molecular weight, cysteine rich, metal binding protein that has a high affinity for, and plays a key role in the detoxication of metals in the IB and П-В groups of the Periodic Table (1, 2). Presence of these metals (ie Zn, Cu, Cd, Hg, Ag), at elevated concentrations increases MT synthesis, and a high percentage of their total concentration in the cell can be found as MT complexes. Of these metals, Ag has the highest affinity for MT The free Ag ion is also known to be extremely toxic to freshwater living animals (3). Recent studies have suggested that disruption of branchial Na/K-ATPase activity is a primary mode of action of Ag toxicity. Ag has been shown to concete for the protein's Mg binding site, displacing the vital Mg that is needed to bind ATP which drives the catalytic activity of the enzyme. In vitro studies have indicated that the Ag-MT complex, however, does not have inhibitory effects on …