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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

The active site of the myosin subfragment-1 ATPase was affinity-labeled with ribose-modified fluorescent analogs of ADP, dADP, CDP, UDP, IDP, and GDP in combination with vanadate, forming a stable myosin-nucleoside diphosphate-vanadate complex that is analogous to the normal myosin-ADP-Pi intermediate [Hiratsuka, T. (1984) J. Biochem. 96, 147-154]. Labeled enzyme was isolated free of unbound analog and vanadate, and fluorescent properties of the fluorophore at the active site were examined. Fluorescence emission and acrylamide quenching studies revealed that the hydrophobicity of environment around the fluorophore and the degree of its burial in the protein vary with the base structure of NDP. It was found that the fluorophore of ADP analog is most buried into the protein, while that of the GDP analog is least buried. The results suggest that the deep burial of ATP into the myosin active site is essential for muscle contraction.
...
PMID:Distinct structures of ATP and GTP complexes in the myosin ATPase. 623 21

The effects of chronic oral administration of ciclazindol on energy balance and brown adipose tissue (BAT) activity were studied in adult rats maintained on a palatable cafeteria diet. Treatment with 1 mg ciclazindol/kg/day produced small, but not significant, reductions in body energy gain and increases in BAT mass and protein content. Administration of 3.4 and 11 mg/kg/day of ciclazindol depressed weight gain and caused a substantial (42%) reduction in body energy gain. These effects were partly due to a lower food intake, but also resulted from a marked decrease in energetic efficiency. Rats treated with 3.4 and 11 mg/kg/day of the drug showed significant increases in BAT protein content, Na+, K+-ATPase activity and mitochondrial proton conductance, assessed from GDP-binding capacity. These results show that the reduced body weight produced by ciclazindol is due to a lower energetic efficiency, which is associated with activation of BAT, and also a depressed food intake.
...
PMID:Influence of chronic administration of ciclazindol on energy balance and brown adipose tissue in adult 'cafeteria'-fed rats. 630 50

Energy balance and brown adipose tissue (BAT) metabolism were studied in rats maintained on stock or 'cafeteria' diet, and injected with either saline or triiodothyronine (T3, 10 micrograms/100 g b.wt./d) for 14 d. Cafeteria-fed rats showed large increases in metabolizable energy intake, energy expenditure and BAT mass, Na+, K+-ATpase activity and mitochondrial GDP binding. In stock fed rats, T3 also stimulated energy intake, metabolic rate and BAT mass and Na+, K+-ATPase activity, but did not affect GDP binding. Hyperthyroidism potentiated the effects of cafeteria feeding on energy expenditure and BAT mass, but BAT Na+, K+-ATPase activity was only slightly higher than that of the euthyroid cafeteria rats, and GDP binding was similar for both groups. These results confirm the involvement of BAT in diet-induced thermogenesis and show that this is potentiated by hyperthyroidism. The data also suggest that thyroid thermogenesis may result, at least partly, from stimulation of BAT.
...
PMID:Influence of thyroid hormone on diet-induced thermogenesis in the rat. 631 7

Vacuoles of sugar-cane suspension cells contained a tonoplast-bound ATPase which was exclusively located on the cytoplasmic side of the vacuole. Vanadate and diethylstilbestrol had little effect on the vacuolar ATPase. ATP was the optimum substrate for the tonoplast ATPase, but there was also evidence for tonoplast-bound GDP-hydrolyzing and GTP-hydrolyzing enzymes which can interfere with the ATPase assay. Other phosphate anhydrides and esters were not hydrolyzed. The addition of MgATP polarized the tonoplast from about 0 mV to an interior-positive value of about +20 mV; MgADP and MgGTP had much less effect; MgGDP and ATP (in the absence of magnesium) had no effect on the membrane potential. The polarization of the tonoplast was insensitive to valinomycin, nigericin, and inhibitors of plasmalemma ATPase, but was strongly reduced by the uncoupler carbonylcyanide m-chlorophenylhydrazone. These data are interpreted as evidence for the action of tonoplast-bound ATPase as a pump which translocates protons into the vacuoles. The activity of the ATPase was highly specific for MgATP2-; the other important ionic states of ATP:ATP4-, HATP3-, MgHATP-, and Mg2ATP neither stimulated nor inhibited. The same was true for Mg2+. Since the protons were not brought to the catalytic site by protonation of the substrate, the tonoplast-ATPase may pick up the proton for translocation from the cytoplasm. The saturation kinetics for MgATP2- hydrolysis were biphasic, the higher affinity ATPase with Km value of 0.7 mM seems to be the physiologically relevant activity.
...
PMID:Role of the ATPase of sugar-cane vacuoles in energization of the tonoplast. 631 33

Treatment of purified ATPase of the thermophilic bacterium PS-3 with the arginine reagent phenylglyoxal or with Woodward's reagent K, gave complete inactivation of the enzyme. The inactivation rates followed apparent first-order kinetics. The apparent order of reaction with respect to inhibitor concentrations gave values near to 1 with both reagents, suggesting that inactivation was a consequence of modifying one arginine or carboxyl group per active site. ADP and ATP strongly protected the thermophilic ATPase against both reagents. GDP and IDP protected less, whilst CTP did not protect. Experiments in which the incorporation of [14C]phenylglyoxal into the enzyme was measured show that extrapolation of incorporation to 100% inactivation of the enzyme gives 8-9 mol [14C]phenylglyoxal per mol ATPase, whilst ADP or ATP prevent modification of about one arginine per mol.
...
PMID:Functional arginine residues and carboxyl groups in the adenosine triphosphatase of the thermophilic bacterium PS-3. 644 37

The short preincubation of submitochondrial particles with low concentrations of ADP in the presence of Mg2+ results in a complete loss of their ATPase and inosine triphosphatase activities. Other nucleoside diphosphates (IDP and GDP) do not affect the ATPase activity. The ADP-inhibited ATPase can be activated in a time-dependent manner by treatment of submitochondrial particles with the enzyme converting ADP into ATP (phosphoenolpyruvate plus pyruvate kinase). The activaton is a first-order reaction with rate constant 0.2 min-1 at 25 degrees C. The rate constant of activation is increased in the presence of ATP up to 2 min-1, and this increase shows saturation kinetics with Km value equal to that for ATPase reaction itself (10(-4) M at 25 degrees C at pH 8.0). The experimental results obtained are consistent with the model where two alternative pathways of ADP dissociation from the inhibitory site of ATPase exist; one is spontaneous dissociation and the second is ATP-dependent dissociation through the formation of the ternary complex between ADP, the enzyme and ATP. ADP-induced inactivation and ATP-dependent activation of ATPase activity of submitochondrial particles is accompanied by the same directed change of their ability to catalyse the ATP-dependent reverse electron transport from succinate to NAD+. The possible implication of the model suggested is discussed in terms of functional role of the inhibitory high-affinity binding site for ADP in the mitochondrial ATPase.
...
PMID:Kinetics of interaction of adenosine diphosphate and adenosine triphosphate with adenosine triphosphatase of bovine heart submitochondrial particles. 645 Dec 17

Nuclei isolated from Yoshida sarcoma cells had activity for conversion of dGTP dependent on DNA synthesis. The ratio of nucleotide generation/generation + incorporation was 0.4 +/0- 0.1, indicating that approx. 40% of the incorporated dGMP was excised. Two lines of evidence indicated the dependence of this activity on DNA synthesis. (1) The activity was observed only in the presence of ATP, which is essential for nuclear DNA synthesis. (2) Inhibitors of DNA synthesis, such as N-ethylmaleimide, aphidicolin, spermine and KCl, also inhibited ATP- or DNA synthesis-dependent dGMP generation. Although nuclei contain nucleoside triphosphatase (N-nucleotidase), this enzyme was not involved appreciably in DNA synthesis-dependent dGMP generation. The reason for this was explained by the following findings. (a) Inhibitors did not decrease dGMP production in the complete absence of DNA synthesis. (b) Inhibitors did not inactivate N-nucleotidase to the same degree as they inhibited DNA synthesis-dependent dGMP generation. (c) Addition of ATP reduced dGMP hydrolysis catalyzed by N-nucleotidase. (d) GDP has no appreciable effect on DNA synthesis-dependent dGMP generation, but had a diluting effect on dGMP production catalyzed by N-nucleotidase. These results show that the pathway of dGMP generation in isolated nuclei was switched on addition of ATP from a N-nucleotidase-catalyzed one to a DNA polymerase-exonuclease-catalyzed one.
...
PMID:Conversion of dNTP to dNMP dependent on DNA synthesis in isolated Yoshida sarcoma nuclei. 706 29

Sedimentation and high performance liquid chromatography studies show that the functional DNA replication helicase of bacteriophage T4 (gp41) exists primarily as a dimer at physiological protein concentrations, assembling from gp41 monomers with an association constant of approximately 10(6) M-1. Cryoelectron microscopy, analytical ultracentrifugation, and protein-protein cross-linking studies demonstrate that the binding of ATP or GTP drives the assembly of these dimers into monodisperse hexameric complexes, which redissociate following depletion of the purine nucleotide triphosphatase (PuTP) substrates by the DNA-stimulated PuTPase activity of the helicase. The hexameric state of gp41 can be stabilized for detailed study by the addition of the nonhydrolyzable PuTP analogs ATP gamma S and GTP gamma S and is not significantly affected by the presence of ADP, GDP, or single-stranded or forked DNA template constructs, although some structural details of the hexameric complex may be altered by DNA binding. Our results also indicate that the active gp41 helicase exists as a hexagonal trimer of asymmetric dimers, and that the hexamer is probably characterized by D3 symmetry. The assembly pathway of the gp41 helicase has been analyzed, and its structure and properties compared with those of other helicases involved in a variety of cellular processes. Functional implications of such structural organization are also considered.
...
PMID:The phage T4-coded DNA replication helicase (gp41) forms a hexamer upon activation by nucleoside triphosphate. 770 92

Guanosine triphosphatase activating protein (GAP) is an important modulator of p21ras (Ras)-dependent signal transduction in mammalian cells and in insulin-induced maturation of Xenopus oocytes. A synthetic octapeptide from the catalytic domain of GAP, residues 899-906 (F899VFLRLIC906), inhibited GAP-stimulated hydrolysis of GTP to GDP by Ras in an in vitro biochemical assay (IC50 = 12 microM). The peptide was assayed for its ability to block insulin- (Ras-dependent) and progesterone- (Ras-independent) induced maturation of stage VI Xenopus laevis oocytes, marked by germinal vesicle breakdown (GVBD). Microinjection of 50 pmol of the peptide inhibited insulin- but not progesterone-induced GVBD by 50%. A 7-residue peptide lacking F899, GAP(900-906)-NH2, failed to inhibit GAP-stimulated GTPase activity and did not block GVBD. Replacement of the cysteine residue at position 906 with methionine resulted in a peptide with prolonged inhibitory activity in the oocyte. Moreover, sequential replacement of specific L-amino acid residues with the corresponding D-amino acids produced a peptide with a two-fold increased half-life after injection into oocytes. None of the peptides tested affected progesterone induced GVBD, suggesting that the modifications did not result in loss of specificity. These studies show that (a) peptides that were able to inhibit GAP-stimulated Ras GTPase activity in vitro were also able to block Ras-dependent GVBD in oocytes, and (b) specific substitutions in these peptides can result in improved stability in oocytes.
...
PMID:Ras-dependent maturation of Xenopus oocytes is blocked by modified peptides of GTPase activating protein (GAP). 778 68


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

---