Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

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

The present work describes experiments that show that far-ultraviolet irradiation induce the inhibition of ATPase activity in both membrane-bound and soluble F1. It was also found that ultraviolet light promotes the release of tightly bound adenine nucleotides from F1-ATPase. Experiments carried out with submitochondrial particles indicate that succinate partially protects against these effects of ultraviolet light. Titration of sulfhydryl groups in both irradiated submitochondrial particles and soluble F1-ATPase indicates that a conformational change induced by photochemical modifications of amino acid residues appears involved in the inactivation of the enzyme. Finally, experiments are described which show that the tyrosine residue located in the active site of F1-ATPase is modified by ultraviolet irradiation.
...
PMID:Inactivation of mitochondrial ATPase by ultraviolet light. 623 89

The oxygen exchange parameters for the hydrolysis of ATP by the F1-ATPase have been determined over a 140,000-fold range of ATP concentrations and a 5,000-fold range of reaction velocity. The average number of water oxygens incorporated into each Pi product ranges from a limit of about 1.02 at saturating ATP concentrations to a limit of about 3.97 at very low ATP concentrations. The latter value represents 400 reversals of hydrolysis of bound ATP prior to Pi dissociation. In accord with the binding change mechanism, this means that ATP binding at one catalytic site increases the off constant of Pi and ADP from another catalytic site by at least 20,000-fold, equivalent to the use of 6 kcal mol-1 of ATP binding energy to promote product release. The estimated rate of reversal of hydrolysis of F1-ATPase-bound ATP to bound ADP + Pi varies only about 5-fold with ATP concentration. The rate is similar that observed previously for reversal of bound ATP hydrolysis or synthesis with the membrane-bound enzyme and is greater than the rate of net ATP formation during oxidative phosphorylation. This adds to evidence that energy input or membrane components are not required for bound ATP synthesis.
...
PMID:Assessment of the rate of bound substrate interconversion and of ATP acceleration of product release during catalysis by mitochondrial adenosine triphosphatase. 623 76

The photoaffinity analog 2-azido-ADP has been used to investigate the high-affinity binding site(s) for ATP on the chloroplast thylakoid membrane. Photophosphorylation of 2-azido-ADP results in the rapid formation of 2-azido-ATP, which remains tightly bound to the membranes after extensive washing. The kinetic parameters of the tight binding of ATP and of 2-azido-ATP are similar (apparent Km = 1-2 microM; maximum extent = 0.2-0.4 nmol/mg of chlorophyll). Ultraviolet irradiation of washed thylakoid membranes containing tightly bound 2-azido-[gamma-32P]ATP induces covalent incorporation of the label exclusively into the beta subunit of the chloroplast coupling factor one. Previous results have shown that the tight binding site for ADP is also located on the beta subunit of the ATP synthase (Czarnecki, J. J., Abbott, M. S., and Selman, B. R. (1983) Eur. J. Biochem. 136, 19-24). To further characterize the tight binding sites for ADP and ATP, the membrane-bound coupling factor has been covalently modified with either tightly bound 2-azido-[gamma-32P]ATP or tightly bound 2-azido-[beta-32P]ADP. The photolabeled beta subunits have been isolated and subjected to partial proteolytic digestion and SDS-gel electrophoresis. The results of these experiments demonstrate that the tight binding sites for ADP and ATP are located on identical portions of beta subunit polypeptide.
...
PMID:Localization of the high-affinity binding site for ATP on the membrane-bound chloroplast ATP synthase. 623 8

The alpha- and beta-subunits of membrane-bound ATP synthase complex bind ATP and ADP: beta contributes to catalytic sites, and alpha may be involved in regulation of ATP synthase activity. The sequences of beta-subunits are highly conserved in Escherichia coli and bovine mitochondria. Also alpha and beta are weakly homologous to each other throughout most of their amino acid sequences, suggesting that they have common functions in catalysis. Related sequences in both alpha and beta and in other enzymes that bind ATP or ADP in catalysis, notably myosin, phosphofructokinase, and adenylate kinase, help to identify regions contributing to an adenine nucleotide binding fold in both ATP synthase subunits.
...
PMID:Distantly related sequences in the alpha- and beta-subunits of ATP synthase, myosin, kinases and other ATP-requiring enzymes and a common nucleotide binding fold. 632 17

The mechanism of beef heart mitochondrial ATPase (F1) was studied using chromium(III)-substituted substrate analogs. Incubation of F1 with monodentate Cr(III)ADP and 32Pi followed by chromatography on Sephadex G-25 resulted in 32Pi counts in the F1 protein peak. The appearance of radioactivity from inorganic phosphate in the protein peak was dependent upon the presence of monodentate Cr(III)ADP and F1, and was inhibited by MgADP. Removal of the enzyme from the reaction mixture containing Cr(III)ADP and 32Pi by acid precipitation followed by chromatography on Sephadex G-10 indicated the net formation and slow release of a radioactive product. High voltage electrophoresis showed that this product was 32Pi . Cr(III)ADP. Incubation of F1 with bidentate Cr(III)ATP also resulted in formation of this product. These results indicated that non-membrane-bound F1 was capable of net synthesis of what may be an ATP synthesis and hydrolysis transition state analog. The F1-dependent formation of the complex was taken as evidence that the soluble ATPase can function in ATP synthesis as well as ATP hydrolysis.
...
PMID:Beef heart mitochondrial adenosine triphosphatase-catalyzed formation of a transition state analog in ATP synthesis. 644 63

The natural mitochondrial ATPase inhibitor (IF1) was modified with a radioactivity labeled heterobifunctional and photosensitive reagent, methyl 4-azido(14C)benzimidate ((14C)MABI). Titration experiments of IF1 by (14C)MABI and tryptic maps of (14C)MABI-IF1 indicated that specific lysine residues in IF1 are preferentially labeled by (14C)MABI. Under appropriate conditions of labeling (1 to 2 lysine residues modified per IF1), MABI-IF1 exhibited the same inhibitory potency as native IF1 on the hydrolytic activity of the coupling factor 1 of mitochondrial ATPase (F1). The same conditions were required for inhibition of F1 by MABI-IF1 and IF1 (slightly acidic pH and presence of ATP and MgCl2). In photolabeling experiments, (14C)MABI-IF1 was used to investigate the localization of IF1 binding sites on F1. Upon photoirradiation, MABI-IF1 bound selectively to the beta subunit of soluble or membrane-bound F1. Adenylyl imidodiphosphate and quercetin, two compounds which partially mimic the inhibitory effect of IF1 on ATPase activity of F1, markedly prevented the binding of (14C)MABI-IF1 to F1; on the other hand, aurovertin, a specific ligand of the beta subunit of F1, did not affect the interaction between (14C)MABI-IF1 and F1. In the absence of light, (14C)MABI-IF1 was used as a reversible radiolabeled ligand with respect to membrane bound F1 to investigate F1-IF1 interactions to inside-out submitochondrial particles as a function of the energy state of the particles. Oxidation of NADH by submitochondrial particles resulted in a decrease of bound (14C)MABI-IF1; the effect was counteracted by antimycin. The data suggested that added (14C)MABI-IF1 is capable of exchanging with IF1 bound to F1 in submitochondrial particles and that the rate and extent of (14C)MABI-IF1 release are triggered by the proton-motive force developed by the particles.
...
PMID:Photoaffinity labeling of mitochondrial adenosine triphosphatase by an azido derivative of the natural adenosine triphosphate inhibitor. 645 97

Mitochondria from Vigna sinensis (L.) Savi cv. Pitiuba contain the polyamines spermine, spermidine, and putrescine. The membrane-bound F1-ATPase from mitochondria of Vigna sinensis is activated by these polyamines at physiological concentrations. The effect of polyamines on the membrane-bound of F1-ATPase is dependent on the concentrations of Na+, K+, MgATP, and Mg2+. Excess Na+ or K+ prevents the activation of the membrane-bound F1-ATPase by spermine and spermidine, but not by putrescine. The most pronounced effects were observed at low MgATP concentrations in the absence of Na+ and K+. At [MgATP] = 0.08 mM, spermine activation of the membrane-bound F1-ATPase was 130%. The membrane-bound F1-ATPase is slightly activated by Mg2+ at lower concentrations and strongly inhibited by Mg2+ at higher concentrations. Activation as well as inhibition is dependent on the substrate MgATP concentration. Although there is competition between Mg2+ and MgATP, the binding sites for these two ligands are different (pseudocompetitive inhibition). The inhibition of the membrane-bound F1-ATPase can be reversed by polyamines. There is evidence that the binding sites for Mg2+ and polyamines are identical. The F1-ATPase detached from the membrane is neither activated by polyamines nor inhibited by Mg2+. Therefore, the binding sites for Mg2+ and polyamines seem to be localized on the membrane.
...
PMID:Regulation of the F-ATPase from mitochondria of Vigna sinensis (L.) Savi cv. Pitiuba by spermine, spermidine, putrescine, Mg2+, Na+, and K+. 645 41

Steady-state velocity studies using a substrate regenerating system showed that efrapeptin, citreoviridin and aurovertin inhibit both membrane-bound and soluble mitochondrial ATPase (coupling factor F1) from Trypanosoma cruzi. Maximal inhibitions of ATP hydrolysis produced by efrapeptin and citreoviridin were 100-93%, while the maximal inhibition produced by aurovertin was 40%. Half-maximal inhibitory concentrations decreased in the order citreoviridin greater than aurovertin greater than efrapeptin. Dissociation constants (KD) for the inhibitor-F1 complex were 81 nM (efrapeptin), 6.6 muM (aurovertin) and 40 muM (citreoviridin); KD values for the membrane-bound F1 were 2-4 fold higher than for soluble F1. Representation of efrapeptin inhibition data in the Hill form yielded straight lines (n = 1) while the same representation of citreoviridin inhibition yielded concave down plots. In contrast to the immediate effect of citreoviridin and aurovertin, efrapeptin inhibition was time-dependent. The onset of inhibition, which was pseudo-first-order with respect to efrapeptin, indicated that ATP may promote the binding of efrapeptin to the enzyme. The kinetics of ATP hydrolysis by T. cruzi ATPase as a function MgATP concentration could be explained by the presence of two substrate sites on the enzyme, interacting in such a way that the binding and catalytic events at one site were conformationally linked to the events at the other site, as with the mammalian ATPase. When the antibiotics were assayed at increasing substrate concentrations, efrapeptin produced a linear, mixed-type inhibition whereas citreoviridin produced a parabolic noncompetitive-type inhibition. The aurovertin effect was unusual since the extent of inhibition was greater at high substrate concentrations. Maximal concentrations of all the assayed antibiotics linearized the biphasic double reciprocal plot of control ATPase activity. Comparison of T. cruzi and mammalian F1 responses to the assayed antibiotics revealed the operation of similar inhibition mechanisms but the T. cruzi enzyme was significantly less sensitive to inhibitors than its mammalian counterpart.
...
PMID:Influence of efrapeptin, aurovertin and citreoviridin on the mitochondrial adenosine triphosphatase from Trypanosoma cruzi. 645 45

A longitudinal cross-over feeding design was used to investigate the relationship of dietary lipid composition to the membrane lipid environment and activity of mitochondrial ATPase in vivo. Rats were fed a polyunsaturated fatty-acid-rich oil (soya-bean oil) for 12 days, crossed-over to a monounsaturated fatty-acid-rich oil (rapeseed oil) for the next 11 days, then returned to soya-bean oil for 11 more days. Additional rats were fed either soya-bean oil or rapeseed oil throughout. Rats fed rapeseed oil had lower rates of ATPase-catalysed ATP/[32P]Pi exchange than rats fed soya-bean oil. Arrhenius plots showed higher transition temperature (Tt) and activation energy (Ea) for rats fed rapeseed oil. Switching from soya-bean oil to rapeseed oil was dynamically followed by changes in the thermotropic and kinetic properties of the mitochondrial ATPase exchange reaction. Returning to soya-bean oil reversed these changes. The rapid and reversible modulation of Tt caused by a change of the type of fat ingested suggests that membrane physicochemical properties are not under rigid intrinsic control but are continually modified by the profile of exogenously derived fatty acids. The studies suggest that in vivo the activity of mitochondrial ATPase is in part determined by dietary lipid via its influence on the microenvironment of the enzyme. The rapidity and ready reversibility of changes observed for this subcellular-membrane-bound enzyme suggest that dietary fatty-acid balance may be an important determinant of other membrane functions in the body.
...
PMID:Dynamic modulation of mitochondrial membrane physical properties and ATPase activity by diet lipid. 645 81

Alanine-scanning mutagenesis was applied to the epsilon subunit of the F1-F0 ATP synthase from E. coli. Nineteen amino acid residues were changed to alanine, either singly or in pairs, between residues 10 and 93. All mutants, when expressed in the epsilon deletion strain XH1, were able to grow on succinate minimal medium. Membranes were prepared from all mutants and assayed for ATP-driven proton translocation, ATP hydrolysis +/- lauryldiethylamine oxide, and sensitivity of ATPase activity to N,N'-dicyclohexylcarbodiimide (DCCD). Most of the mutants fell into 2 distinct classes. The first group had inhibited ATPase activity, with near normal levels of membrane-bound F1, but decreased sensitivity to DCCD. The second group had stimulated ATPase activity, with a reduced level of membrane-bound F1, but normal sensitivity to DCCD. Membranes from all mutants were further characterized by immunoblotting using 2 monoclonal antibodies. A model for the secondary structure of epsilon and its role in the function of the ATP synthase has been developed. Some residues are important for the binding of epsilon to F1 and therefore for inhibition. Other residues, from Glu-59 through Glu-70, are important for the release of inhibition by epsilon that is part of the normal enzyme cycle.
...
PMID:Alanine-scanning mutagenesis of the epsilon subunit of the F1-F0 ATP synthase from Escherichia coli reveals two classes of mutants. 755 84


<< Previous 1 2 3 4 5 6 7 8 9 10

---