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:3.6.1.25 (triphosphatase)
1,529 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The electric birefringence technique was used to investigate the steady-state birefringence, the orientational relaxation time, and the orientation mechanism of pig heart mitochondrial F1 adenosine-5'-triphosphatase (F1-ATPase). The electrooptical properties of this enzyme in solution were studied as functions of pH, protein concentration, and applied electric field. The F1-ATPase exhibits a surprising negative electric birefringence with a specific Kerr constant of -1.5 X 10(-3) esu cgs. The field-independent relaxation time was found to be 0.65 +/- 0.05 microseconds, corresponding to a rotational diffusion constant of 2.55 X 10(5) s-1. The overall size and shape of F1-ATPase have been calculated from both translational and rotational diffusion constants. The enzyme may be assumed to be an oblate ellipsoid of revolution with dimensions of about 170 X 170 X 70 A. The orientation mechanism of F1-ATPase was analyzed by fitting experimental birefringence rising curves with theoretical rising functions. The ratio of the permanent to induced dipole moment is found to be very high; therefore, the birefringence of F1-ATPase is due to a strong permanent dipole moment in a direction perpendicular to the long axes of the particle. These particular electric properties can be explained by the oligomeric structure of the protein and seem likely to play a role in its mechanism of functioning.
...
PMID:Structural aspects and orientation mechanism of mitochondrial F1 adenosinetriphosphatase. Evidence for a negative electric birefringence due to a permanent moment perpendicular to the long axes of the particle. 287 17

We have studied the apparent kinetic parameters of the ecto-nucleotide triphosphatase from CLL B lymphocytes and compared them to blood and tonsillar B and T cells. The Vmax of the ecto-ATPase activity in CLL B lymphocytes, was 65 +/- 10 fmol Pi/cell per 30 min compared to 37 +/- 2.1 in blood B lymphocytes, and 8.5 +/- 1.7 in blood T lymphocytes. The ATPase of membranes prepared from CLL, tonsillar B and T, and blood T lymphocytes had a relationship among the cell types similar to that seen in intact cells. However, no difference in the km for ATP, .17 mM, or the km for magnesium, .15 mM was found in the ecto-ATPase of CLL lymphocytes as compared to blood or tonsillar B cells. The ectoenzyme of CLL cells hydrolyzed GTP, ITP, CTP, and UTP as well as ATP. Further, ATP added to an enzyme assay containing an alternative nucleotide did not result in increased phosphate release. Nucleotide acceptance of blood B and T lymphocytes was very similar to that of CLL B cells. ATP inhibited phosphate release when present in excess of magnesium in both CLL and blood B lymphocytes. These data indicate that there is greater ectonucleotide triphosphatase activity in tonsillar and blood B lymphocytes, including CLL, as compared either to blood or tonsillar T lymphocytes. However, CLL cells showed no qualitative difference from blood or tonsillar B cells in ectonucleotidase activity. Thus, the higher activity in CLL cells is "B cell-like" and might reflect, also, their maturation stage or monoclonal origin.
...
PMID:Ecto-nucleotide triphosphatase activity of human lymphocytes: studies of normal and CLL lymphocytes. 293 42

Escherichia coli helicase II, product of the uvrD gene, is a single-stranded DNA-dependent nucleoside 5'-triphosphatase with helicase activity. As a DNA-dependent ATPase, helicase II translocates processively along single-stranded DNA (S. W. Matson, unpublished results). The direction of translocation has been determined using a helicase assay that directly measures the ability of helicase II to catalyze the displacement of a labeled DNA fragment from one end of a single-stranded linear DNA molecule. The translocation of helicase II along single-stranded DNA is unidirectional and in the 3' to 5' direction with respect to the DNA strand on which the enzyme is bound. A kinetic analysis of the displacement of a labeled DNA fragment annealed to a linear single-stranded DNA molecule is also consistent with unidirectional translocation in the 3' to 5' direction. These results are contrary to results previously obtained using an indirect helicase assay (Kuhn, B., Abdel-Monem, M., Krell, H., and Hoffmann-Berling, H. (1979) J. Biol. Chem. 254, 11343-11350).
...
PMID:Escherichia coli helicase II (urvD gene product) translocates unidirectionally in a 3' to 5' direction. 294 37

A comparison of kinetic parameters (Km(app) and V) of hydrolysis by heavy meromyosin of natural (ATP and ITP) and modified nucleoside triphosphates showed that in the K+, EDTA-ATPase conformation the enzyme exhibited a higher selectivity towards the structure of the substrate nucleoside moiety than in the case of the Ca2+-stimulated nucleoside triphosphatase activity. In the presence of Ca2+, all the N1- and N6-substituted analogs of ATP as well as ITP, etheno-ATP and the dialdehyde derivative of ATP were hydrolyzed at a high rate irrespective of their markedly decreased affinity for heavy meromyosin. In the presence of K+, EDTA the ATPase activity showed a tendency for a total decrease of the analog affinity for nucleoside triphosphates, i.e., the impossibility of tight binding of the substrate phosphate residues to the protein in the absence of bivalent cations, which was concomitant with an increase in the hydrolysis rate. However, it was found that only in N1-substituted analogs any appreciable changes in the substrate properties were absent. All the other nucleoside triphosphates tested (N6-carboxy-methoxy-ATP, N6-(N'-acetylaminoethoxy)-ATP, etheno-ATP, ITP and the dialdehyde derivative of ATP having a rupture in the ribose ring) lost their ability to be hydrolyzed by heavy meromyosin. The experimental results as well as the literature data are suggestive of differences in the spatial structure of the active center in two different myosin conformations associated with a high catalytic activity, i.e., K+, EDTA-ATPase and Ca2+-ATPase.
...
PMID:[Increased substrate selectivity during transition from Ca2+-activated to K+,EDTA-activated nucleoside triphosphatase activity of heavy meromyosin]. 296 18

The incision of damaged DNA by the Escherichia coli UvrABC endonuclease requires ATP hydrolysis. Although the deduced sequence of the UvrB protein suggests a putative ATP binding site, no nucleoside triphosphatase activity is demonstrable with the purified UvrB protein. The UvrB protein is specifically proteolyzed in E. coli cell extracts to yield a 70 kD fragment, referred to as UvrB*, which has been purified and is shown to possess a single-strand DNA dependent ATPase activity. Substrate specificity and kinetic analyses of UvrB* catalyzed nucleotide hydrolysis indicate that the stimulation in DNA dependent ATPase activity following formation of the UvrAB complex results from the activation of the normally sequestered UvrB associated ATPase. Using nucleotide analogues, it can be shown that this activity is essential to the DNA incision reaction carried out by the UvrABC complex.
...
PMID:Involvement of a cryptic ATPase activity of UvrB and its proteolysis product, UvrB* in DNA repair. 1661 84

We have studied the effects of vanadate on the rotational motion of the calcium adenosine-triphosphatase (Ca-ATPase) from sarcoplasmic reticulum (SR), using saturation-transfer electron paramagnetic resonance (ST-EPR). Vanadate has been proposed to act as a phosphate analogue and produce a stable intermediate state similar to the phosphoenzyme. This study provides evidence about the physical state of this intermediate. In particular, since ST-EPR provides a sensitive measure of microsecond protein rotational mobility, and hence of protein-protein association, these studies allowed us to ask (a) whether the vanadate-induced protein association observed in electron micrographs of SR vesicles also occurs under physiological (as opposed to fixed, stained, or frozen) conditions and (b) whether vanadate-induced changes in protein association also occur under conditions sufficient for enzyme inhibition but not for the production of large arrays detectable by electron microscopy (EM). At 5 mM decavanadate, a concentration sufficient to crystallize the ATPase on greater than 90% of the membrane surface area in EM, ST-EPR showed substantial immobilization of the spin-labeled protein, indicating protein-protein association in the unstained vesicles. Conventional EPR spectra of lipid probes showed that lipid hydrocarbon chain mobility is unaffected by decavanadate-induced protein crystallization in SR, suggesting that changes in protein-protein contacts do not involve the lipid hydrocarbon region. At 5 mM monovanadate, a concentration sufficient to inhibit the ATPase but not to form crystals detectable by EM, no changes were observed in ST-EPR or conventional EPR spectra of either protein or lipid.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Effects of vanadate on the rotational dynamics of spin-labeled calcium adenosinetriphosphatase in sarcoplasmic reticulum membranes. 302 Nov 93

Escherichia coli helicase II has been purified to near homogeneity from cells harboring a multicopy plasmid containing the structural gene for helicase II, uvrD. In this paper a detailed description of the single-stranded DNA-dependent nucleoside 5'-triphosphatase and helicase reactions catalyzed by helicase II is presented. The results of this study suggest that nucleoside 5'-triphosphate hydrolysis provides the energy required for translocation of the enzyme along single-stranded DNA. Measurements of the rate of ATP hydrolysis using a variety of single-stranded DNAs of known structure and length suggest a processive translocation mechanism for helicase II. Single-stranded DNA coated with either Escherichia coli single-stranded DNA binding protein (SSB) or bacteriophage T4 gene 32 protein fails to support helicase II ATPase activity. Moreover, helicase II is apparently unable to displace a molecule of bound SSB protein from single-stranded DNA when it is encountered in the process of translocation along a single-stranded DNA effector. The helicase reaction has been characterized using an in vitro strand displacement helicase assay. The helicase reaction requires concomitant nucleoside 5'-triphosphatase hydrolysis that is satisfied by the hydrolysis of either rATP or dATP. As the length of duplex DNA present in the partial duplex helicase substrate is increased from 71 base pairs to 343 base pairs, the fraction of duplex DNA molecules that are unwound by helicase II decreases in the absence of any accessory proteins. However, the total number of base pairs of duplex DNA unwound depends primarily on the amount of enzyme added to the helicase reaction and not on the length of the duplex DNA present in the partial duplex DNA substrate. These data suggest the number of base pairs of duplex DNA unwound is directly proportional with the concentration of helicase II in the reaction mixture. In addition, the rate of the unwinding reaction is independent of the length of the duplex DNA available for unwinding. Helicase II has been shown to dissociate from single-stranded DNA molecules infrequently acting as an ATPase. However, the enzyme dissociates from partial duplex helicase substrates more frequently. This suggests a more distributive reaction mechanism on duplex DNA than was observed on single-stranded DNA substrates. The fraction of 343-base pair partial duplex DNA molecules unwound by helicase II can be increased by the addition of appropriate concentrations of E. coli SSB to the reaction. This suggests that helicase II and SSB may act in a concerted reaction to unwind duplex DNA.
...
PMID:DNA helicase II of Escherichia coli. Characterization of the single-stranded DNA-dependent NTPase and helicase activities. 302 63

The distribution of ATPase activity in the asynchronous flight muscles of Calliphora erythrocephala (Diptera) was studied at a fine structural level, using preparations of teased fibers, both unfixed and after brief fixation in hydroxyadipaldehyde, incubated in a medium for the histochemical demonstration of myosin or actomyosin ATPase. In relaxed fibrils, activity was found confined to the A bands and was absent from the H zones as well as from the Z and I band regions. At high magnification, deposits of final product, lead phosphate, appeared primarily related to the thick filaments, or to short lateral extensions from them. Evidence was gathered which indicated that this enzyme activity was that of a triphosphatase which did not act on dinucleoside or non-nucleoside substrates.
...
PMID:The localization of myofibrillar ATPase activity in the flight muscles of the blowfly, Calliphora erythrocephala. 422 Oct 34

A biochemical and cytochemical study has been made of the distribution of ATPase in mature and differentiating phloem cells of Nicotiana tabacum and of the substrate specificity and effects of fixation on enzyme activity. Homogenates of unfixed leaf midveins and midveins fixed in formaldehyde-glutaraldehyde were assayed for enzyme activity by determining the amount of P(i), liberated per milligram of protein from various substrates in a 30 min period at pH 7.2. In fresh homogenates, hydrolysis of ATP was not significantly different from that of ITP, CTP, and UTP. Hydrolysis of GTP was slightly higher than that of ATP. ATP hydrolysis by fresh homogenates was 17% more extensive than that of ADP, 76% more extensive than that of 5'-AMP, and was inhibited by fluoride and p-chloromercuribenzoate (PCMB). There was little or no hydrolysis of the competitive inhibitors 2'- and 3'-AMP nor with the alternate substrates p-nitrophenylphosphate (PNP) or beta-glycerophosphate (beta-GP). In homogenates of material fixed in formaldehyde-glutaraldehyde for 1(1/4) h, ATPase activity was 13% preserved. Hydrolysis of ATP by fixed homogenates was not significantly different from that of ADP, 5'-AMP, ITP, CTP, and GTP. Hydrolysis of UTP was lower. Fluoride and PCMB inhibited fixed ATPase activity. The results of cytochemical localization experiments using a lead phosphate precipitation technique were in agreement with the biochemical results. Similar localization patterns were obtained with the nucleoside triphosphates ATP, CTP, GTP, ITP, and UTP. Activity was also localized with ADP and 5'-AMP but not with the competitive inhibitors 2'- and 3'-AMP, nor with PNP or beta-GP. Little or no reaction product was deposited in other controls incubated without substrate or with substrate plus fluoride, PCMB, or N-ethylmaleimide. ATPase activity was demonstrated chiefly at the plasma membrane of mature and differentiating phloem cells and was associated with the P-protein of mature sieve elements. It is suggested that the phloem transport system derives its energy from the demonstrated nucleoside triphosphatase activity.
...
PMID:A biochemical and cytochemical study of adenosine triphosphatase activity in the phloem of Nicotiana tabacum. 427 79

Electrophorus electroplax microsomes were examined for Ca2+- and Mg2+-dependent ATPase activity. In addition to the previously reported low-affinity ATPase, a high-affinity (Ca2+,Mg2+)-ATPase was found. At low ATP and Mg2+ concentrations (200 microM or less), the high-affinity (Ca2+,Mg2+)-ATPase exhibits an activity of 18 nmol Pi mg-1 min-1 with 0.58 microM Ca2+. At higher ATP concentrations (3 mM), the low-affinity Ca2+-ATPase predominates, with an activity of 28 nmol Pi mg-1 min-1 with 1 mM Ca2+. In addition, Mg2+ can also activate the low-affinity ATPase (18 nmol Pi mg-1 min-1). The high-affinity ATPase hydrolyzes ATP at a greater rate than it does GTP, ITP, or UTP and is insensitive to ouabain, oligomycin, or dicyclohexylcarbodiimide inhibition. The high-affinity enzyme is inhibited by vanadate, trifluoperazine, and N-ethylmaleimide. Added calmodulin does not significantly stimulate enzyme activity; rinsing the microsomes with EGTA does not confer calmodulin sensitivity. Thus the high-affinity ATPase from electroplax microsomes is similar to the (Ca2+,Mg2+)-ATPase reported to be associated with Ca2+ transport, based on its affinity for calcium and its response to inhibitors. The low-affinity enzyme hydrolyzes all tested nucleoside triphosphates, as well as diphosphates, but not AMP. Vanadate and N-ethylmaleimide do not inhibit the low-affinity enzymes. The low-affinity enzyme reflects a nonspecific nucleoside triphosphatase, probably an ectoenzyme.
...
PMID:Characterization of the Ca2+- and Mg2+-dependent ATPases in Electrophorus electroplax microsomes. 613 30


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

---