Specific binding of inorganic mercury to Na- K-ATPase in rat liver plasma membrane and signal transduction

Specific binding of Hg to ouabain-sensitive Na-K-ATPase of rat liver plasma membrane was demonstrated with a K of 2.64¥10 and B of 1.6nmole mg protein. The binding of mercury to the enzyme also causes significant inhibition of the enzyme, which is greater than its ouabain sensitivity. In the cytosol Hg binding to reduced glutathione (GSH) is stimulated by GSH-S-transferase (GST), the activity of which was found to be significantly enhanced by 15mM Na and 10mM Hg. It is proposed that the transport of Hg2 inside the cell takes place by increased dissociation of Hg from the membrane due to greater avidity of Hg towards cytosolar GSH binding. The GSH-Hg complex enters the nucleus where it dissociates to bind the metal response element (MRE) of the metallothionein (MT) gene to induce MT transcription.