Uncoupler-stimulated Na+ pump and its possible role in the halotolerant bacterium, Ba.
In cells of Ba1 suspended in K salt as the osmoticum, the respiratory rate declined by 80% between the pH values of 6.5 and 8.5. Catalytic amounts of Na+ ions prevented this drop. The possibility that Na+ exerted its effect by an influence on proton fluxes across the membrane (Na+/H+ exchange) was explored. Addition of catalytic amounts of Na+ ions to cells respiring at pH 8.5 elicited an influx of protons and, as a result, the delta pH across the membrane became diminished. delta psi (membrane potential) was not affected by Na+. At pH 6.5, Na+ caused no proton influx. FCCP (carbonylcyanide-p-trifluoromethoxyphenylhydrazone) collapsed delta psi, but the Na+-dependent proton influx observed at pH 8.5 became enhanced, leading to an inversion of delta pH (more acid inside). When a Na salt was used as the osmoticum, delta pH of reversed polarity was generated by respiration also in the absence of FCCP. Respiring, inverted membrane vesicles responded to a Na+ pulse essentially as the intact cells. Based on the above and some additional findings it is suggested that these Na+-dependent effects are suited to prevent a raise in the intracellular pH over the level which hinders the respiratory activity. It may also play a role in the regulation of intracellular Na salt content.
D000255:Adenosine Triphosphate / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology; D006358:Hot Temperature; D007700:Kinetics; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D011190:Potassium Cyanide / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers; D014475:Uncoupling Agents / Q000494:pharmacology*
D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D014475:Uncoupling Agents; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000431:Ethanol; D000255:Adenosine Triphosphate; D012964:Sodium; D011190:Potassium Cyanide