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

Specific binding of Hg2+ to ouabain-sensitive Na+-K+-ATPase of rat liver plasma membrane was demonstrated with a K-a of 2.64 x 10(9) and B-max of 1.6 nmole mg(-1) 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 Hg2+ binding to reduced glutathione (GSH) is stimulated by GSH-S-transferase (GST), the activity of which was found to be significantly enhanced by 15 mM Na+ and 10 mM Hg2+, It is proposed that the transport of Hg2+ inside the cell takes place by increased dissociation of Hg2+ from the membrane due to greater avidity of Hg2+ 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.