title: Organization of thiol groups of electric-eel electric-organ sodium-plus-potassium ion-stimulated adenosine triphosphatase studied with bifunctional reagents.
abstract: The reactions of three bifunctional thiol-blocking reagents of differing cross-linking spans and two monofunctional thiol-blocking reagents with the Na+ + K+-stimulated ATPase of the electric-eel electric organ were examined. 1,5-Difluoro-2,4-dinitrobenzene with a cross-linking span of 0.3--0.5 nm (3--5 A) and high solubility in non-polar solvent was the most efficient inhibitor of enzyme activity; thus essential thiol groups exist in a non-polar environment and are approx. 0.3--0.5 nm (3--5 A) from their nearest thiol-group neighbours. Ligands promoting phosphorylation of the Na+ + K+-stimulated ATPase decreased the number of thiol groups bridged by 1,5-difluoro-2,4-dinitrobenzene and by 4,4'-difluoro-3,3'-dinitrodiphenyl sulphone [0.7--1.0 nm (7--10 A) span]. Phosphorylation is associated with a conformational change in the enzyme.
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004557:Electric Organ / Q000201:enzymology*; D004593:Electrophorus; D008024:Ligands; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013439:Sulfhydryl Reagents / Q000494:pharmacology
chemical_list: D003432:Cross-Linking Reagents; D008024:Ligands; D013439:Sulfhydryl Reagents; D000254:Sodium-Potassium-Exchanging ATPase