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 Ka of 2.64 x 10(9) and Bmax 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.
Bhattacharya
S
S
Department of Zoology, Visva Bharati University, Santiniketan, India.
Bose
S
S
Mukhopadhyay
B
B
Sarkar
D
D
Das
D
D
Bandyopadhyay
J
J
Bose
R
R
Majumdar
C
C
Mondal
S
S
Sen
S
S
D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D007553:Isotope Labeling; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D008628:Mercury / Q000378:metabolism / Q000633:toxicity; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics
D010042:Ouabain; D008668:Metallothionein; D012964:Sodium; D005982:Glutathione Transferase; D000254:Sodium-Potassium-Exchanging ATPase; D008628:Mercury; D005978:Glutathione