351. Inhibition of N-ethylmaleimide of the MgATP-driven proton pump of the chromaffin granules
- Author
-
Torgeir Flatmark, Sissel Vik Berge, Eystein S. Husebye, and Martin Grønberg
- Subjects
Proton channel ,ATPase ,Biophysics ,Ethylmaleimide ,Biochemistry ,chemistry.chemical_compound ,Adenosine Triphosphate ,Structural Biology ,ATP hydrolysis ,Organelle ,Adrenal Glands ,Genetics ,medicine ,Animals ,heterocyclic compounds ,Chromaffin Granules ,Molecular Biology ,Adrenal medulla ,Membrane potential ,N,N-Dicyclohexylcarbodiimide ,Adenosine Triphosphatases ,biology ,N-Ethylmaleimide ,Cell Biology ,Hydrogen-Ion Concentration ,Proton pump ,Kinetics ,Proton-Translocating ATPases ,medicine.anatomical_structure ,chemistry ,Chromaffin System ,N-ethylmaleimide ,biology.protein ,H+-ATPase ,Cattle - Abstract
The thiol reagent N-ethylmaleimide (NEM) completely inhibits the proton pump activity of the H+-ATPase in chromaffin granule 'ghosts' at concentrations which only partly (approximately 20%) inhibit the Mg2+-dependent ATP hydrolysis. Half-maximal inhibition was obtained at approximately 13 microM NEM as compared to 18 microM for the classical proton channel inhibitor N,N'-dicyclohexylcarbodiimide (DCCD), and the apparent stoichiometry of the inhibitors at complete inhibition was NEM : DCCD congruent to 1 : 2. HIgh concentrations of NEM (greater than 100 microM) induce a dissipation of the transmembrane potential generated by MgATP. These findings establish NEM as a valuable proton channel inhibitor in chromaffin granules and explain the rather complex effect of NEM previously reported for catecholamine accumulation in this organelle.
- Published
- 1982