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Inhibition by N ‐ethylmaleimide of the MgATP‐driven proton pump of the chromaffin granules
Author(s) -
Flatmark Torgeir,
Grønberg Martin,
Husebye Eystein,
Vik Berge Sissel
Publication year - 1982
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(82)81074-0
Subject(s) - chemistry , n ethylmaleimide , biophysics , atp hydrolysis , atpase , diaphragm pump , proton pump , proton , biochemistry , stereochemistry , enzyme , biology , nanotechnology , materials science , physics , quantum mechanics , micropump
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 (∼20%) inhibit the Mg 2+ ‐dependent ATP hydrolysis. Half‐maximal inhibition was obtained at ∼13 μM NEM as compared to 18 μM for the classical proton channel inhibitor N,N' ‐dicyclohexylcarbodiimide (DCCD), and the apparent stoichiometry of the inhibitors at complete inhibition was NEM:DCCD ⋍ 1 : 2. High concentrations of NEM (⪢100 μM) 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.