title: Location of an oligomycin-insensitive and magnesium ion-stimulated adenosine triphosphatase in rat spleen mitochondria.
abstract: 1. When rat spleen mitochondria are incubated with oxidizable substrates, added MgCl2 (greater than 150 muM free concentration) markedly stimulates state-4 respiration and lowers both the respiratory control and ADP/O ratios; this effect is reversible on addition of excess of EDTA. 2. With [gamma-32P]ATP as substrate, an Mg2+-stimulated ATPase (adenosine triphosphate) was identified in the atractyloside-insensitive and EDTA-accessible space of intact rat spleen mitochondria. 3. Oligomycin has no effect on the activity of the Mg2+-stimulated ATPase at a concentration (2.0mug/mg of protein) that completely inhibits the atractyloside-sensitive reaction. Of the two ATPase activities, only the atracytoloside sensitive reaction is stimulated (approx. 40%) by dinitrophenol. 4. On digitonin fractionation the atractyloside-insensitive Mg2+-stimulated ATPase co-purifies with the outer membrane-fraction of rat spleen mitochondria, whereas (as expected) the atractylosidesensitive activity co-purifies with the inner-membrane plus matrix fraction. 5. Stoicheiometric amounts of ADP and Pi are produced as the end products of ATP hydrolysis by purified outer-membrane fragments; no significant AMP production is detected during the time-course of the reaction. 6. The outer-membrane ATPase is present in rat kidney cortex and heart mitochondria as well as in spleen, but is absent from rat liver, thymus, brain, lung, diaphragm and skeletal muscle.
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000302:isolation & purification*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001278:Atractyloside / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002499:Centrifugation, Density Gradient; D004072:Digitonin; D004140:Dinitrophenols / Q000494:pharmacology; D004579:Electron Transport / Q000187:drug effects; D007527:Isoenzymes; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008928:Mitochondria / Q000201:enzymology* / Q000648:ultrastructure; D009840:Oligomycins / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D013154:Spleen / Q000201:enzymology* / Q000648:ultrastructure
chemical_list: D004140:Dinitrophenols; D007527:Isoenzymes; D009840:Oligomycins; D001278:Atractyloside; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D008274:Magnesium; D004072:Digitonin; D002118:Calcium