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 question of the possible identity of catalytic and regulatory proton pathways in the chloroplast FoF1 ATPase has been studied using different energy-transfer inhibitors. Venturicidin, a reversible inhibitor of Fo, affects neither the delta mu H(+)-dependent thiol reduction of the membrane-bound chloroplast ATPase nor its ability to be activated by the proton gradient. It seems therefore to block only the proton flow required by the catalytic function of the enzymes. Venturicidin, however, also slows down the deactivation of the thiol-reduced ATPases during uncoupled ATP hydrolysis, following a delta mu H+ activation, but phloridzin, a reversible F1 inhibitor, has the same effect. Tentoxin, an irreversible F1 inhibitor, decreases the rate of ATP hydrolysis but does not affect the rate of deactivation. These findings suggest that catalytic and regulatory H(+)-binding sites are different. No distinction can be made, if any, between protons involved in unmasking the thiol-sensitive groups of F1 and in activating the enzyme. The effect of venturicidin and phloridzin on the deactivation is consistent with an inhibitory effect of newly formed--by ATP hydrolysis--ADP molecules, which might affect the enzyme without passing through the medium. Phosphate at millimolar concentration has an effect similar to low concentrations of phloridzin and venturicidin, probably by a simple back-reaction effect.
...
PMID:An attempt to discriminate catalytic and regulatory proton binding sites in membrane-bound, thiol-reduced chloroplast ATPase. 131 60

Treatment of isolated, latent chloroplast ATPase with pyridoxal-5-phosphate (pyridoxal-P) in presence of Mg2+ causes inhibition of dithiothreitol-activated plus heat-activated ATP hydrolysis. The amount of [3H]pyridoxal-P bound to chloroplast coupling factor 1 (CF1) was estimated to run up to 6 +/- 1 pyridoxal-P/enzyme, almost equally distributed between the alpha- and beta-subunits. Inactivation, however, is complete after binding of 1.5-2 pyridoxal-P/CF1, suggesting that two covalently modified lysines prevent the activation of the enzyme. ADP as well as ATP in presence of Mg2+ protects the enzyme against inactivation and concomittantly prevents incorporation of a part of the 3H-labeled pyridoxal-P into beta- and alpha-subunits. Phosphate prevents labeling of the alpha-subunit, but has only a minor effect on protection against inactivation. The data indicate a binding site at the interface between the alpha- and beta-subunits. Cleavage of the pyridoxal-P-labeled subunits with cyanogen bromide followed by sequence analysis of the labeled peptides led to the detection of Lys beta 359, Lys alpha 176 and Lys alpha 266, which are closely related to proposed nucleotide-binding regions of the alpha- and beta-subunits.
...
PMID:Inactivation of chloroplast H(+)-ATPase by modification of Lys beta 359, Lys alpha 176 and Lys alpha 266. 183 78

Upon incubation with trypsin, the adenosine-5'-triphosphatase (ATPase) activity of the nucleotide-depleted F1 is first rapidly and slightly activated and then slowly inactivated. The first phase is simultaneous with the conversion of the alpha subunit into an alpha' fragment which migrates between alpha and beta on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The second phase is related to the proteolysis of the three main subunits, alpha', beta, and gamma. Preincubation of the enzyme with low concentrations of adenosine 5'-diphosphate (ADP) or adenosine 5'-triphosphate (ATP) does not modify the slight increase of activity but efficiently prevents the inactivation induced by trypsin. The alpha leads to alpha' conversion is not affected whereas the further proteolysis of alpha', beta, and gamma does not occur. On the contrary, even high concentrations of GDP only slightly lower the trypsin-induced inactivation. The presence of endogenous tightly bound nucleotides also partially lowers the sensitivity to trypsin since F1 is less rapidly inactivated and proteolyzed than the nucleotide-depleted F1. Phosphate, at high concentrations, both slows down the first phase of activation and simultaneous alpha leads to alpha' conversion and prevents the second phase of inactivation and proteolysis of the main subunits. Pretreatment of the nucleotide-depleted F1 with trypsin under conditions where the ATPase activity is largely inhibited only slightly modifies, however, the hysteretic behavior of the enzyme: the ADP binding and the concomitant hysteretic inhibition of the residual activity are not markedly diminished. The purified ATPase-ATP synthase complex binds very few ADP's and is not hysteretically inhibited. Its ATPase activity is rapidly activated but not further inhibited by trypsin. Preincubation of the complex with ADP does not modify the effects of trypsin.
...
PMID:Use of trypsin to monitor conformational changes of mitochondrial adenosinetriphosphatase induced by nucleotides and phosphate. 622 Jul 37

An N-ethylmaleimide-sensitive phosphate transport protein has been isolated from rat liver mitochondria, substantially purified, and reconstituted into phospholipid vesicles. Purified inner mitochondrial membrane vesicles depleted of F1-ATPase by urea treatment proved to be the most satisfactory starting material. Treatment of these membrane vesicles with Triton X-100 resulted in solubilization of the phosphate transport protein. Further purification was achieved using hydroxylapatite powder. Polyacrylamide gel electrophoresis of the purified fraction in sodium dodecyl sulfate indicated the presence of two Coomassie blue-staining bands with apparent Mr's of 30,000 and 35,000. Labeling of the 35,000 Mr band by the Pi transport inhibitor diazobenzene sulfonate was reduced markedly by prior treatment of the mitochondria with the inhibitor N-ethylmaleimide. The purified fraction containing both proteins could be reconstituted into liposomes prepared from purified asolectin. Phosphate efflux from these vesicles was inhibited by N-ethylmaleimide, by the impermeant mercurial agent, p-chloromercuribenzoate, and by diazobenzene sulfonate. Treatment of the purified fraction with N-ethylmaleimide prior to incorporation into liposomes resulted in a reconstituted system incapable of catalyzing Pi efflux. These studies summarize the first detailed attempt to purify the Pi/H+ transport system from rat liver mitochondria and emphasize the need to commence the purification with purified inner membrane vesicles depleted of F1-ATPase. In addition, these studies show that the final fraction contains a reconstitutively active transport system which when incorporated into phospholipid vesicles has its essential sulfhydryl groups oriented outward. Finally, it is shown that the purified fraction also contains a 30,000 Mr component.
...
PMID:Isolation and reconstitution of an N-ethylmaleimide-sensitive phosphate transport protein from rat liver mitochondria. 630 81

Sulfite stimulates the rate of ATP hydrolysis by the ATP synthase in chromatophores of Rhodobacter capsulatus. The stimulated activity is inhibited by oligomycin. The activation takes place also in uncoupled chromatophores. The activation consists in an increase of about 12-15-fold of the Vmax for the ATP hydrolysis reaction, while the Km for MgATP is unaffected at 0.16+/-0.03 mM. The dependence of Vmax on the sulfite concentration follows a hyperbolic pattern with half maximum effect at 12 mM. Sulfite affects the ability of the enzyme in translocating protons. Concomitant measurements of the rate of ATP hydrolysis and of ATP-induced protonic flows demonstrate that at sulfite concentrations of greater than 10 mM the hydrolytic reaction becomes progressively uncoupled from the process of proton translocation. This is accompanied by an inhibition of ATP synthesis, either driven by light or by artificially induced ionic gradients. ATP synthesis is totally inhibited at concentrations of at least 80 mM. Sulfite interferes with the mechanism of activation by delta muH+. Low concentrations of this anion (< or = 2 mM) prevent the activation by delta muH+. At higher concentrations a marked stimulation of the activity prevails, regardless of the occurrence of a delta muH+ across the membrane. Phosphate at millimolar concentrations can reverse the inhibition by sulfite. These experimental results can be simulated by a model assuming multiple and competitive equilibria for phosphate or sulfite binding with two binding sites for the two ligands (for sulfite K1S = 0.26 and K2S = 37 mM, and for phosphate K1P = 0.06 and K2P = 4.22 mM), and in which the state bound only to one sulfite molecule is totally inactive in hydrolysis. The competition between phosphate and sulfite is consistent with the molecular structures of the two ligands and of the enzyme.
...
PMID:Sulfite stimulates the ATP hydrolysis activity of but not proton translocation by the ATP synthase of Rhodobacter capsulatus and interferes with its activation by delta muH+. 934 8

The interaction between sulfite, an efficient Mg2+-dependent F1-ATPase activator, and chloroplast CF1-ATPase was studied. The sulfite anion was shown to inhibit ADP and ATP binding to the noncatalytic sites of CF1. The stimulating activity of sulfite persists when all noncatalytic sites are nucleotide-occupied. Phosphate, a competing candidate for binding to CF1 catalytic sites, suppresses this activity. These results support the suggestion that the stimulation of Mg2+-dependent ATPase activity of CF1 is caused by sulfite binding to its catalytic sites.
...
PMID:Interaction of sulfite with the noncatalytic and catalytic sites of chloroplast coupling factor cf1. 1140 48

Residues responsible for phosphate binding in F(1)F(0)-ATP synthase catalytic sites are of significant interest because phosphate binding is believed linked to proton gradient-driven subunit rotation. From x-ray structures, a phosphate-binding subdomain is evident in catalytic sites, with conserved betaArg-246 in a suitable position to bind phosphate. Mutations betaR246Q, betaR246K, and betaR246A in Escherichia coli were found to impair oxidative phosphorylation and to reduce ATPase activity of purified F(1) by 100-fold. In contrast to wild type, ATPase of mutants was not inhibited by MgADP-fluoroaluminate or MgADP-fluoroscandium, showing the Arg side chain is required for wild-type transition state formation. Whereas 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) inhibited wild-type ATPase essentially completely, ATPase in mutants was inhibited maximally by approximately 50%, although reaction still occurred at residue betaTyr-297, proximal to betaArg-246 in the phosphate-binding pocket. Inhibition characteristics supported the conclusion that NBD-Cl reacts in betaE (empty) catalytic sites, as shown previously by x-ray structure analysis. Phosphate protected against NBD-Cl inhibition in wild type but not in mutants. The results show that phosphate can bind in the betaE catalytic site of E. coli F(1) and that betaArg-246 is an important phosphate-binding residue.
...
PMID:Mutagenesis of residue betaArg-246 in the phosphate-binding subdomain of catalytic sites of Escherichia coli F1-ATPase. 1515 Feb 66

To assess the restorative capacity of isolated avocado (Persea americana) fruit mitochondria, the organelles were first aged in the absence of an energy source at 25 degrees C for several hours until respiratory control and oxidative phosphorylation were greatly diminished or totally lost. Energy-linked functions were then gradually restored over a period of several hours after the addition of substrate. Restoration of respiratory control resulted from both an increase in state 3 and a decrease in state 4 respiratory rates. Either alpha-ketoglutarate or succinate served as restorants, each with distinctive rates of recovery in state 3 and state 4 respiration. ATP also served as a restorative agent but not as effectively as metabolizable substrate. ATP synthase activity was modulated by stress and restoration but neither the extent nor the rate of change was sufficient to constrain state 3 rates. Orthophosphate was released from the mitochondria during substrate-deprived stress. Restoration of phosphorylation preceded that of RC with phosphate uptake and phosphorylation being evident immediately upon the addition of substrate. During restoration [(32)P]orthophosphate was incorporated into several organic fractions: phospholipid, ATP, a trichloroacetic acid-precipitable mitochondrial fraction, and an organophosphate that accumulated in the medium in relatively large amounts. The organophosphate was tentatively identified as a hexosephosphate. Incorporation into ATP and the putative hexosephosphate continued unabated beyond the point of maximum restoration. Phosphate metabolism thus appears to be a necessary but not sufficient precondition for mitochondrial restoration and maintenance. Based on the recovery kinetics of the various phosphorylated components, the mitochondrial-bound fraction appears to be most directly linked with restoration. Results are discussed with reference to specific characteristics and components of self-restoration and to possible underlying mechanisms. We suggest that a degree of self-restoration is consistent with the quasi-autonomous nature of mitochondria and that this intrinsic capacity may be pivotal to the respiratory climacteric in senescent fruit cells and to cellular homeostasis in general.
...
PMID:Metabolically driven self-restoration of energy-linked functions by avocado mitochondria: general characteristics and phosphorylative aspects. 1666 96

Adenosine triphosphate (ATP) is used as a general energy source by all living cells. The free energy released by hydrolyzing its terminal phosphoric acid anhydride bond to yield ADP and phosphate is utilized to drive various energy-consuming reactions. The ubiquitous F(1)F(0) ATP synthase produces the majority of ATP by converting the energy stored in a transmembrane electrochemical gradient of H(+) or Na(+) into mechanical rotation. While the mechanism of ATP synthesis by the ATP synthase itself is universal, diverse biological reactions are used by different cells to energize the membrane. Oxidative phosphorylation in mitochondria or aerobic bacteria and photophosphorylation in plants are well-known processes. Less familiar are fermentation reactions performed by anaerobic bacteria, wherein the free energy of the decarboxylation of certain metabolites is converted into an electrochemical gradient of Na(+) ions across the membrane (decarboxylation phosphorylation). This chapter will focus on the latter mechanism, presenting an updated survey on the Na(+)-translocating decarboxylases from various organisms. In the second part, we provide a detailed description of the F(1)F(0) ATP synthases with special emphasis on the Na(+)-translocating variant of these enzymes.
...
PMID:ATP synthesis by decarboxylation phosphorylation. 1804 5

The role of alphaPhe-291 residue in phosphate binding by Escherichia coli F1F0-ATP synthase was examined. X-ray structures of bovine mitochondrial enzyme suggest that this residue resides in close proximity to the conserved betaR246 residue. Herein, we show that mutations alphaF291D and alphaF291E in E. coli reduce the ATPase activity of F1F0 membranes by 350-fold. Yet, significant oxidative phosphorylation activity is retained. In contrast to wild-type, ATPase activities of mutants were not inhibited by MgADP-azide, MgADP-fluoroaluminate, or MgADP-fluoroscandium. Whereas, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) inhibited wild-type ATPase essentially completely, ATPase in mutants was inhibited maximally by approximately 75%, although reaction still occurred at residue betaTyr-297, proximal to alphaPhe-291 in the phosphate-binding pocket. Inhibition characteristics supported the conclusion that NBD-Cl reacts in betaE (empty) catalytic sites, as shown previously by X-ray structure analysis. Phosphate protected against NBD-Cl inhibition in wild-type but not in mutants. In addition, our data suggest that the interaction of alphaPhe-291 with phosphate during ATP hydrolysis or synthesis may be distinct.
...
PMID:Role of alphaPhe-291 residue in the phosphate-binding subdomain of catalytic sites of Escherichia coli ATP synthase. 1824 62


1 2 Next >>

---