H+ transport by reconstituted gastric (H+ + K+)-ATPase.
Gastric (H+ + K+)-ATPase was reconstituted into artificial phosphatidylcholine/cholesterol liposomes by means of a freeze-thaw-sonication technique. Upon addition of MgATP, active H+ transport was observed, with a maximal rate of 2.1 mumol X mg-1 X min-1, requiring the presence of 100 mM K+ at the intravesicular site. However, in the absence of ATP an H+-K+ exchange with a maximal rate of 0.12 mumol X mg-1 X min-1 was measured, which could be inhibited by the well-known ATPase inhibitors vanadate and omeprazole, giving the first evidence of a passive K+-H+ exchange function of gastric (H+ + K+)-ATPase. An Na+-H+ exchange activity was also measured, which was fully inhibited by 1 mM amiloride. Simultaneous reconstitution of Na+/H+ antiport and (H+ + K+)-ATPase could explain why reconstituted ATPase appeared less cation-specific than the native enzyme (Rabon, E.C., Gunther, R.B., Soumarmon, A., Bassilian, B., Lewin, M.J.M. and Sachs, G. (1985) J. Biol. Chem. 260, 10200-10212).
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002463:Cell Membrane Permeability; D017506:H(+)-K(+)-Exchanging ATPase; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008081:Liposomes; D008564:Membrane Potentials; D009853:Omeprazole; D011188:Potassium / Q000378:metabolism; D011522:Protons; D013552:Swine; D014639:Vanadium / Q000494:pharmacology
D001562:Benzimidazoles; D008081:Liposomes; D011522:Protons; D014639:Vanadium; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase; D009853:Omeprazole; D011188:Potassium