Sodium and proton transport in Mycoplasma gallisepticum.
When washed cells of Mycoplasma gallisepticum were incubated at 37 degrees C in 250 mM 22NaCl, the intracellular Na+ increased, and the K+ decreased. The addition of glucose to these Na+-loaded cells caused Na+ efflux and K+ uptake (both ions moving against concentration gradients). This effect of glucose was blocked by the ATPase inhibitor dicyclohexylcarbodiimide, which prevents the generation of a proton motive force in these cells. In additional experiments, Na+ extrusion was studied by diluting the 22Na+-loaded cells into Na+-free media and following the loss of 22Na+ from the cells. Glucose stimulated 22Na+ extrusion in such cells by a dicyclohexylcarbodiimide-sensitive mechanism. Proton movement was studied by measuring the pH gradient across the cell membrane with the 9-aminoacridine fluorescence technique. Glucose addition to cells preincubated with cations other than Na+ resulted in cell alkalinization (which was prevented by dicyclohexylcarbodiimide). This observation is consistent with the operation of a proton-extruding ATPase. When glucose was added to Na+-loaded cells and diluted into Na+-free media, intracellular acidification was observed, followed several minutes later by a dicyclohexylcarbodiimide-sensitive alkalinization process. The initial acidification was probably due to the operation of an Na+-H+ antiport, since Na+ exit was occurring simultaneously with H+ entry. When Na+-loaded cells were diluted into Na+-containing media, the subsequent addition of glucose resulted in a weak acidification, presumably due to H+ entry in exchange for Na+ (driven by the ATPase) plus a continuous passive influx of Na+. All of the data presented are consistent with the combined operation of an ATP-driven proton pump and an Na+ -H+ exchange reaction.
D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009174:Mycoplasma / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000378:metabolism
D002712:Chlorides; D013757:Tetraethylammonium Compounds; D004024:Dicyclohexylcarbodiimide; D019789:Tetraethylammonium; D012964:Sodium; D012413:Rubidium; D011188:Potassium