H+-ATPase

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H+-ATPase

A ubiquitously expressed enzyme transporter present in the plasma membrane, as well as in endomembrane organelles—vacuoles, lysosomes, endosomes, the Golgi apparatus, chromaffin granules and coated vesicles—which acidifies intracellular compartments in eukaryotic cells. Acidification is necessary for such intracellular processes as protein sorting, protein degradation and coupled transport, zymogen activation, receptor-mediated endocytosis and synaptic vesicle proton gradient generation; it also plays a role in bone reabsorption and in sperm motility and maturation. H+-ATPase is a multisubunit complex composed of two domains: a cytosolic V1 domain responsible for ATP hydrolysis and a transmembrane V0 domain responsible for protein translocation.

Mechanisms of regulating H+-ATPase activity:
• Recycling of H+-ATPase-containing vesicles to and from the plasma membrane;
• Glucose-sensitive assembly/disassembly of the holoenzyme complex.
 
Molecular pathology
H+-ATPase mutations in the A3 gene cause recessive osteopetrosis; they have been implicated in tumour metastasis.
References in periodicals archive ?
Salt-induced transcriptional activation of V-ATPase subunits A, B, E, and c have been shown in common ice plant [2, 6, 19].
Endogenous oscillations of the transcript amounts of subunit-c of the V-ATPase of Mesembryanthemum crystallinum with harmonic frequency resonances under continuous illumination.
The V-ATPase creates an electrochemical proton gradient across the tonoplast, which is used for secondary-active solute uptake mediated by specific transporters, as well as is pivotal to pH homeostasis of the cytoplasm.
Distribution and Characteristics of V-ATPase in Plants
The activity of V-ATPase can be distinguished from other [H.
Amongst various phytohormones, the V-ATPase is stimulated only by phenylacetic acid, the other auxins have no effect, whereas [GA.
V-ATPase pumps the protons into membrane surrounded intercellular compartments at the expense of hydrolysis of ATP.
The V-ATPase is closely related to bacterial and mitochondrial F-ATPase, and they both share structural and functional similarities [51].
In recent times, the existence of various isoforms of different subunits of V-ATPase has also been demonstrated.
There is sufficient evidence to suggest that V-ATPase shows functional analogy with the F-ATPase in its mechanism of action [63].
The sequence information for the various subunits of V-ATPase is available from two plant species, Arabidopsis thaliana [23] and Mesembryanthemum crystallinum [24].
V-ATPase is believed to play a significant role in cancer cell biology, including glycolytic metabolism, drug/radiation resistance, and invasive/metastatic potential.