Regulation and reversibility of vacuolar H(+)-ATPase.
Arabidopsis thaliana vacuolar H(+)-translocating pyrophosphatase (V-PPase) was expressed functionally in yeast vacuoles with endogenous vacuolar H(+)-ATPase (V-ATPase), and the regulation and reversibility of V-ATPase were studied using these vacuoles. Analysis of electrochemical proton gradient (DeltamuH) formation with ATP and pyrophosphate indicated that the proton transport by V-ATPase or V-PPase is not regulated strictly by the proton chemical gradient (DeltapH). On the other hand, vacuolar membranes may have a regulatory mechanism for maintaining a constant membrane potential (DeltaPsi). Chimeric vacuolar membranes showed ATP synthesis coupled with DeltamuH established by V-PPase. The ATP synthesis was sensitive to bafilomycin A(1) and exhibited two apparent K(m) values for ADP. These results indicate that V-ATPase is a reversible enzyme. The ATP synthesis was not observed in the presence of nigericin, which dissipates DeltapH but not DeltaPsi, suggesting that DeltapH is essential for ATP synthesis.
Hirata
T
T
Division of Biological Sciences, Institute of Scientific and Industrial Research, Osaka University, Osaka 567-0047, Japan.
Nakamura
N
N
Omote
H
H
Wada
Y
Y
Futai
M
M
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017360:Arabidopsis / Q000201:enzymology; D001692:Biological Transport; D002451:Cell Compartmentation; D015971:Gene Expression Regulation, Enzymologic; D007425:Intracellular Membranes / Q000201:enzymology; D018942:Macrolides; D018892:Proton-Motive Force; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011755:Pyrophosphatases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D025262:Vacuolar Proton-Translocating ATPases; D014617:Vacuoles / Q000201:enzymology*
D000900:Anti-Bacterial Agents; D018942:Macrolides; D011994:Recombinant Proteins; C040929:bafilomycin A1; D000255:Adenosine Triphosphate; D011755:Pyrophosphatases; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases