ATPase proton translocating

Vacuolar-type proton translocating ATPase is a heter-eomeric protein complex, which appears to translocate two protons across the vesicle membrane for each ATP molecule that is hydrolyzed, generating chemical (ApH) and electrical (A ) gradients. Although the ATPases present on different classes of intracellular vesicle have... 

Synaptic vesicles isolated from brain exhibit four distinct vesicular neurotransmitter transport activities one for monoamines, a second for acetylcholine, a third for the inhibitory neurotransmitters GABA and glycine, and a fourth for glutamate [1], Unlike Na+-dependent plasma membrane transporters, the vesicular activities couple to a proton electrochemical gradient (A. lh+) across the vesicle membrane generated by the vacuolar H+-ATPase ( vacuolar type proton translocating ATPase). Although all of the vesicular transport systems rely on ApH+, the relative dependence on the chemical and electrical components varies (Fig. 1). The... 

Complex V (ATP Synthase, Mitochondrial Proton-Translocating ATPase)... 

Vance, J.E., eds.), pp. 116-142, Benjamin/Cummings Publishing Co., Menlo Park, California. Senior, A.E. (1988). ATP synthesis by oxidative phosphorylation. Physiological Rev. 68, 177-230. Senior, A.E. (1990). The proton-translocating ATPase of Esherichia colt. Ann. Rev. Biophys. Chem. 19,7- 1. 

Osteoclasts are multinucleated cells derived from pluripotent hematopoietic stem cells. Osteoclasts possess an apical membrane domain, exhibiting a ruffled border that plays a key role in bone resorption (Figure 48-12). A proton-translocating ATPase expels protons across the ruffled border into the resorption area, which is the microenvironment of low pH shown in the figure. This lowers the local pH to 4.0 or less, thus increasing the solubility of hydroxyapatite and allowing demineralization to occur. Lysosomal acid proteases are released that digest the now accessible matrix proteins. 

Phosphatase Hydrolysis of phosphate Translocation of ATPases linked to cation Inorganic pyrophosphatase (pyrophosphate orthophosphate + P043-) Glucose-6-phosphatase Fructose-1,6-bisphosphatase Alkaline phosphatase Phosphoprotein phosphatase (Na+, K+)-ATPase (Mg2+, Ca2+)-ATPase Proton-translocating ATPase Zn2+ Zn2+ Sodium pump Calcium pump H+ pump... 

Extensive studies have been carried out on the proton-translocating ATPase of mitochondrial, bacterial and chloroplast membranes. This enzyme can also function in reverse to exploit the electrochemical potential of protons built up by respiration for the synthesis of ATP from ADP and P .298 The synthesis of ATP can be effected by the application of external electrical pulses to the ATPase vesicles in suspension with submitochondrial particles, showing that the diffusion potential of the protons (ApH) is not used. The yield of ATP was linearly dependent on the number of pulses.299... 

Leng, X. H., Nishi, T., and Forgac, M. (1999). Transmembrane topography of the 100-kDa a subunit (Vphlp) of the yeast vacuolar proton-translocating ATPase./. Biol. Chem. 274, 14655-14661. 

CF, coupling factor 1, the hydrophilic portion of the proton-translocating ATPase of chloroplasts... 

Serrano, R. (1988). Structure and function of proton translocating ATPase in plasma membranes of plants and fungi. Biochim. Biophys. Acta 947,1-28. 

With regard to possible mechanisms for the regeneration of NAD(P) and the possible concomitant synthesis of ATP in thermoacidophiles, an ATPase involved in oxidative phosphorylation in S. acidocaldarius has been found [17-19]. However, no proton-translocating ATPase has been identified in Tp. acidophilum, although a membrane-bound enzyme, proposed to function as a sulphate-exporting translocase, has been reported [20]. 

One of these complexes, the ATP synthase, sometimes called the proton-translocating ATPase, is present in closely similar forms in all energy-transducing membranes. When the complex is assembled in the membrane it catalyzes a hydrolysis or synthesis of ATP which is coupled to the obligatory translocation of protons across the membrane. 

The -ATPase described here, called FgF, differs greatly from another proton translocating ATPase discovered in fungal plasma membranes, etc. [18]. The latter. 

An Mg -dependent, proton-translocating ATPase activity has been identified and characterized in surface membrane from L. donovani promastigotes (55). The enzyme has a pH optimum of 6.5, and is inhibited by orthovanadate and dicyclohexylcar-bodiimide. Membrane vesicles, devoid of attached cytoskeletal elements, were shown to contain ATPase activity. These vesicles were incubated in the presence of acridine orange and ATP to demonstrate the proton-pumping activity of the surface membrane ATPase. This experiment revealed an ATP-driven acidification of the vesicles internal space in those vesicles with an inside-out orientation. 

Zilberstein, D. and Dwyer, D. M. (1988) Identification of a surface membrane proton-translocating ATPase in promastigotes of the parasitic protozoan Leishmania donovani. Biochem. J. 256 13-21. 

As described before, the pH of an endosome is acidified by proton-translocating ATPases (18) that depend on the stage of endosomal development. This pH gradient is a key trigger in the design of membrane-disruptive polymers, which could enhance the endosomal escape of bioactive agents. 

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