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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)

1. Preincubation of MgATP submitochondrial particles with EDTA or Tris.HCl liberated a measurable amount of ATPase inhibitor that could be rapidly purified using only trichloroacetic acid precipitation and heat treatment. 2. In spite of the emergence of high ATPase activity, a considerable amount of ATPase inhibitor was left in the particles. Comparative analysis of other submitochondrial preparations indicated that only AS-particles were effectively depleted. 3. The high ATPase activity of inhibitor-deficient particles, was labile at low temperature provided that the exposure to cold was done in the presence of MgATP. Other nucleotides could not substitute for ATP. Glycerol inhibited and salts enhanced the cold inactivation of membrane-bound F1-ATPase. Isolation of F1-ATPase from cold-inactivated particles yielded a soluble preparation of correspondingly lower activity. 4. It is concluded that together with the increase of ATPase activity, the ATP-dependent cold lability of membrane-bound F1-ATPase and the dislocation of ATPase inhibitor at non operative sites reveal the extent of ATPase complex disorganization.
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PMID:Cold lability of membrane-bound F1-ATPase. 14 42

The effects of glycerol and methanol upon beef heart mitochondrial ATPase (F1) were studied. Glycerol was found to be a potent reversible inhibitor of the F1-catalyzed hydrolysis of ATP and ITP. The inhibition of ATP hydrolysis was linear with respect to glycerol concentrations, while that of ITP was not. From the temperature dependence of Vmax for F1-catalyzed ATP and ITP hydrolysis in glycerol or methanol solutions, the energy of activation and the enthalpy of activation were calculated. The inhibitory effect of ADP on F1 hydrolytic activity was studied in three solvent systems (totally aqueous, 20% methanol, and 20% glycerol). Compared to the aqueous system, methanol decreased the potency of ADP as an inhibitor, and glycerol enhanced the potency.
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PMID:Kinetic and thermodynamic properties of beef heart mitochondrial ATPase: effect of co-solvent systems. 645 17

Pressure stability of the complex formed between F1-ATPase and the inhibitor protein (IP) was studied in the membrane-bound and soluble, purified forms of beef-heart mitochondrial enzymes. A latent preparation of submitochondrial particles (SMP-MgATP) initially exhibits low hydrolytic activity. Dissociation of IP increases the activity about 10-fold. This increase occurs in parallel with an increase in sensitivity to pressure inactivation. The membrane-bound, latent IP-F1-ATPase complex is activated 2.5-fold when incubated at a pressure of 1.7 kbar, suggesting dissociation of IP. A fully active preparation of submitochondrial particles depleted of IP (AS-particles) is highly pressure labile when compared with the latent form. In the absence of IP, soluble purified F1-ATPase is also inactivated by pressure. In contrast, the soluble IP-F1-ATPase complex is very resistant to pressure, as evidenced by enzymatic and fluorescence studies. Based on the pressure-titration experiments, binding of IP stabilizes the F1-ATPase complex by 1.54 kcal per mole of complex. The substrate MgATP confers additional protection on both preparations only in the presence of IP. Glycerol appears to prevent dissociation of IP and therefore protects SMP-MgATP from pressure inactivation. Our results demonstrate that in addition to its regulatory role in catalysis, IP stabilizes the structure of the F1-ATPase complex. The pressure-induced dissociation of IP from F1-ATPase and its prevention by glycerol suggest that nonpolar in addition to electrostatic interactions are important for the binding of IP to the regulatory site.
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PMID:Pressure effects on the interaction between natural inhibitor protein and mitochondrial F1-ATPase. 944 19

The isolation of the chloroplast ATP synthase complex (CF(0)-CF(1)) and of CF(1) from Dunaliella bardawil is described. The subunit structure of the D. bardawil ATPase differs from that of the spinach in that the D. bardawil alpha subunit migrates ahead of the beta subunit and epsilon-migrates ahead of subunit II of CF(0) when separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The CF(1) isolated from D. bardawil resembles the CF(1) isolated from Chladmydomonas reinhardi in that a reversible, Mg(2+)-dependent ATPase is induced by selected organic solvents. Glycerol stimulates cyclic photophosphorylation catalyzed by D. bardawil thylakoid membranes but inhibits photophosphorylation catalyzed by spinach thylakoid membranes. Glycerol (20%) also stimulates the rate of ATP-P(i) exchange catalyzed by D. bardawil CF(0)-CF(1) proteoliposomes but inhibits the activity with the spinach enzyme. The ethanol-activated, Mg(2+)-ATPase of the D. bardawil CF(1) is more resistant to glycerol inhibition than the octylglucoside-activated, Mg(2+)-ATPase of spinach CF(1) or the ethanol-activated, Mg(2+)-dependent ATPase of the C. reinhardi CF(1). Both cyclic photophosphorylation and ATP-P(i) exchange catalyzed by D. bardawil CF(0)-CF(1) are more sensitive to high concentrations of NaCl than is the spinach complex.
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PMID:Purification and Characterization of a Glycerol-Resistant CF(0)-CF(1) and CF(1)-ATPase from the Halotolerant Alga Dunaliella bardawil. 1666 7