Regulation and Reversibility of Vacuolar H+-ATPase

T. Hirata, N. Nakamura, H. Omote, Y. Wada, and M. Futai

J. Bio.Chem. Vol. 275 (1): 286-389, 2000


Fungal and yeast vacuoles possess the V-ATPase as the sole proton pump, whereas those of higher plants contain V-ATPase and a proton translocating pyrophosphatase (V-PPase). Arabidopsis thaliana vacuolar H+-translocating pyrophosphatase (V-PPase) can be expressed in yeast as a functional vacuolar proton pump with endogenous vacuolar H+-ATPase (V-ATPase), and the regulation and reversibility of electrochemical proton gradient (DpH). In this study, we demonstrated that V-ATPase can synthesize ATP coupled with DmH generated by V-PPase and that proton translocation by the two pumps is not strictly regulated by DpH. In addition, the ATP synthesis was sensitive to bafilomycin A1 which gives two Km values for ADP and it was not observed in the addition of nigericin which dissipates DpH not DY, indicating that V-ATPase is a reversible enzyme and DpH is essential for ATP synthesis.


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