This vacuole based atpases are found in the eukaryotic endomembrane system [vacuoles, golgi apparatus, endosomes, lysosomes, clathrin-coated vesicles (transport external substances inside the cell)], plant tonoplasts, the plasma membrane of prokaryotes, and certain specialized eukaryotic cells. V-atpases hydrolyse atp to drive a proton pump, but cannot work in reverse to synthesize atp.
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V-ATPase
V-type ATPases are more like the F0-F1-type ATPase than the P-type ATPase in that they do not form phosphorylated intermediates, are quite large (>400kDa), assume a lollipop shape and are electrogenic.
From: Cell Physiology Source Book (Fourth Edition), 2012
Related terms:
LysosomesPhagosomeProton PumpOsteoclastAdenosine TriphosphateGradientsProteinGeneAdenosine TriphosphataseTonoplast
Modulation of Coupling Efficiency
V-ATPase activity can also be controlled by modulating the ratio of proton transport to ATP hydrolysis (Moriyama and Nelson, 1988). In some organelles such as the vacuole of the lemon fruit, which maintain a pH of near 2, coupling is generally high, but varies with the seasonal frequency (Muller et al., 1999). In vitro, mild proteolysis or high levels of ATP have been shown to affect mammalian V-ATPase coupling efficiency (Adachi et al., 1990; Arai et al., 1989). Moreover, yeast V-ATPase complexes containing different a subunits have been shown to differ in their coupling efficiency, suggesting that these subunits may play a role in this type of regulation (Kawasaki-Nishi et al., 2001).