title: Localization of endogenous ATPases at the nerve terminal.
abstract: We have investigated the localization of a set of intrinsic ATPase activities associated with purified synaptic plasma membranes and consisting of (a) a Mg2+-ATPase; (b) an ATPase active at high concentrations of Ca2+ in the absence of Mg2+ (CaH-ATPase); (c) a Ca2+ requiring Mg2+-dependent ATPase (Ca + Mg)-ATPase, stimulated by calmodulin (Ca-CaM-ATPase); (d) a Ca2+-dependent ATPase stimulated by dopamine (DA-ATPase); and (e) the ouabain-sensitive (Na + K)-ATPase. The following results were obtained: (1) All ATPases are largely confined to the presynaptic membrane; (2) the DA-, (Ca + Mg)-, (Ca-CaM)-, and (Na + K)-ATPases are oriented with their ATP hydrolysis sites facing the synaptoplasm; (3) the Mg- and CaH-ATPases are oriented with their ATP hydrolysis sites on the junctional side of the presynaptic membrane and are therefore classified as ecto-ATPases of as yet unknown function.
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis*; D000818:Animals; D004072:Digitonin / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009411:Nerve Endings / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012503:Saponins / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D013574:Synaptosomes / Q000201:enzymology
chemical_list: D012503:Saponins; D010042:Ouabain; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D004072:Digitonin