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Query: EC:3.6.3.14 (ATP synthase)
 7,042 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Evidence that the F1F0 ATPase (ATP synthase) of alkalophilic Bacillus firmus RAB is localized exclusively on the cytoplasmic membrane was obtained by immunogold electron microscopy using a highly specific polyclonal antibody against the beta subunit of Escherichia coli F1F0 ATPase. The energetic problem faced by cells of B. firmus RAB growing oxidatively at pH 10.5 despite a low protonmotive force across the cytoplasmic membrane cannot, therefore, be circumvented by localization of energy transducing functions on hypothetical internal membranes.
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PMID:Immunoelectron microscopic localization of the F1F0 ATPase (ATP synthase) on the cytoplasmic membrane of alkalophilic Bacillus firmus RAB. 252 7

At the optimal pH for growth (pH 10.5), alkalophilic Bacillus firmus RAB, an obligate aerobe, exhibits normal rates of oxidative phosphorylation despite the low transmembrane proton electrochemical gradient, about -60 mV (delta psi = -180 mV and delta pH = +120 mV). This bioenergetic problem might be resolved by use of an Na+ coupled ATP synthase; otherwise an F1F0-ATPase must be able to utilize low driving forces in this organism. The ATPase activity was extracted from everted membrane vesicles by low ionic strength treatment and purified to homogeneity by hydrophobic interaction chromatography and sucrose density gradient centrifugation. The ATPase preparation had the characteristic F1-ATPase subunit structure, with Mr values of 51,500 (alpha), 48,900 (beta), 34,400 (gamma), 23,300 (delta), and 14,500 (epsilon); the identity of the alpha and beta subunits was confirmed by immunoblotting with anti-beta of Escherichia coli and anti-B. firmus RAB F1. Methanol and octyl glucoside, agents that stimulated the low basal membrane ATPase activity 10- to 12-fold, dramatically elevated the MgATPase activity of the purified F1, more than 150-fold, to 50 mumol min-1 mg protein-1. Anti-F1 inhibited membrane ATPase activity greater than or equal to 80%. The membranes exhibited no Na+-stimulated or vanadate-sensitive ATPase activity when prepared in the absence or presence of Na+ or ATP. These findings, which are consistent with previous studies, establish that in alkalophilic bacteria, ATP hydrolysis, and presumably ATP synthesis is catalyzed by an F1F0-ATPase rather than a Na+ ATPase.
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PMID:The membrane ATPase of alkalophilic Bacillus firmus RAB is an F1-type ATPase. 287 76

Starved whole cells of the obligately alkalophilic Bacillus firmus RAB synthesize ATP upon addition of L-malate at pH 9.0 as expected of an aerobic organism that grows oxidatively on nonfermentable carbon sources at pH values as high as 11.0. The current study was a detailed examination of the perplexing inability of such cells to exhibit ATP synthesis in response to a valinomycin-mediated potassium diffusion potential at pH 9.0. While there were minor differences in the patterns of generation of the potential and the proton influx that accompanies its generation in the three different buffering systems employed, the magnitude of the transmembrane electro-chemical potential of protons was at least as high as pH 9.0 as at pH 7.0. Nevertheless, a diffusion potential consistently energized ATP synthesis at pH 7.0 but not at 9.0; these findings were independent of the presence or absence of Tris or of Na+. By contrast, the artificial electron donor ascorbate, in the presence of phenazine methosulfate, energized ATP synthesis by the starved whole cells at both pH values. The same phenomenon, i.e., efficacy of a respiration-derived potential but not of a diffusion potential at pH 9.0, was demonstrated in ADP + Pi-loaded membrane vesicles. On the other hand, electrogenic Na+-coupled solute transport could be energized by both ascorbate/phenazine and methosulfate and a diffusion potential in the vesicles at pH 9.0. The results are discussed in connection with models of a localized path of proton flow between proton pumps and the ATP synthase.
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PMID:Failure of an alkalophilic bacterium to synthesize ATP in response to a valinomycin-induced potassium diffusion potential at high pH. 400 68