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

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

9-(2-Phosphonylmethoxyethyl)adenine (PMEA) is a potent and selective inhibitor of retrovirus (i.e., human immunodeficiency virus) replication in vitro and in vivo. Uptake of PMEA by human MT-4 cells and subsequent conversion to the mono- and diphosphorylated metabolites (PMEAp and PMEApp) are dose-dependent and occur proportionally with the initial extracellular PMEA concentrations. Adenylate kinase is unable to phosphorylate PMEA. However, 5-phosphoribosyl-1-pyrophosphate synthetase directly converts PMEA to PMEApp with a Km of 1.47 mM and a Vmax that is 150-fold lower than the Vmax for AMP. ATPase, 5'-phosphodiesterase, and nucleoside diphosphate kinase are able to dephosphorylate PMEApp to PMEAp, albeit to a much lower extent than the dephosphorylation of ATP. PMEApp has a relatively long intracellular half-life (16-18 hr) and has a much higher affinity for the human immunodeficiency virus-specified reverse transcriptase than for the cellular DNA polymerase alpha (Ki/Km: 0.01 and 0.60, respectively). PMEApp is at least as potent an inhibitor of human immunodeficiency virus reverse transcriptase as 2',3'-dideoxyadenosine 5'-triphosphate. Being an alternative substrate to dATP, PMEApp acts as a potent DNA chain terminator, and this may explain its anti-retrovirus activity.
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PMID:Intracellular metabolism and mechanism of anti-retrovirus action of 9-(2-phosphonylmethoxyethyl)adenine, a potent anti-human immunodeficiency virus compound. 170 39

Two DNA helicases from calf thymus nuclei have been purified and characterized. The two proteins, designated as nuclear DNA helicase I and II, were copurified on Bio-Rex 70, DEAE-Sepharose, phosphocellulose and subsequently separated from each other on a heparin-Sepharose column. Final purification of DNA helicase I was achieved on single-stranded DNA-cellulose and that of DNA helicase II on ATP-agarose. On denaturing polyacrylamide gels, nuclear DNA helicase I displayed two polypeptide bands of 170 and 200 kDa; nuclear DNA helicase II also consisted of two bands, in this case of 100 and 130 kDa. Both enzymes catalyzed the unwinding of a DNA primer from a single-stranded DNA template but had different nucleotide requirements for their energy supply. While nuclear DNA helicase I preferred to hydrolyze ATP or dATP to support its unwinding activity, nuclear DNA helicase II could utilize all four rNTPs or dNTPs, though ATP or dATP were still preferred to other nucleotides. ADP, AMP, or adenosine 5'-O-(thiotriphosphate) could not be used by either enzyme in the unwinding reactions. A divalent cation was essential for activity of both enzymes. Nuclear DNA helicase I required 3-5 mM Mg2+ or 1 mM Mn2+ for optimal unwinding. In contrast, nuclear DNA helicase II displayed high activity even at very low concentrations of Mg2+. Nuclear DNA helicase I was stimulated by NaCl, KCl, or potassium acetate up to concentrations of 150 mM; in contrast, nuclear DNA helicase II was strongly inhibited at salt concentrations over 75 mM. Both DNA helicases had an associated ATPase activity. However, while the ATPase activity of nuclear DNA helicase I was stimulated only in presence of single-stranded DNA, the ATPase activity of the nuclear DNA helicase II was stimulated by single-stranded DNA and, even more efficiently, by RNA. Finally, the translocation of both DNA helicases had a polarity from 3' to 5' with respect to the single-stranded DNA template to which the enzymes were bound. A comparison of these DNA helicases with the other reported mammalian DNA helicases will be given. The significance of the association of the two DNA helicases during the process of the purification will be discussed.
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PMID:Purification and characterization of two DNA helicases from calf thymus nuclei. 171 63

Vaccinia virus RNA polymerase requires the vaccinia early transcription factor, VETF, for the in vitro initiation of transcription at early gene promoters in a reaction requiring ATP hydrolysis. VETF binds specifically to early gene promoters and has an associated DNA-dependent ATPase activity. The effect of ATP on the interaction of VETF with the promoter for the vaccinia growth factor gene promoter has been examined. ATP had no marked effect on the steady-state level of promoter binding but dramatically affected the kinetics of dissociation of VETF from the promoter. The half-life of the VETF-promoter complex was greatly reduced in the presence of ATP. The destabilization of the complex was specific for ATP and dATP, consistent with the substrate specificity of the VETF-associated ATPase. ADP or the non-hydrolyzable ATP analog adenylyl-imidodiphosphate did not destabilize the complex suggesting that ATP hydrolysis is obligatory for dissociation. These findings provide a link between the promoter binding and ATPase activities associated with VETF and suggest that the ATP-dependent dissociation of the VETF-promoter complex is an important event in the transcription of vaccinia virus early genes.
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PMID:A role for ATP hydrolysis in vaccinia virus early gene transcription. Dissociation of the early transcription factor-promoter complex. 186 72

We have purified a DNA helicase from calf thymus to apparent homogeneity by monitoring the activity with a strand displacement assay. DNA helicase followed the DNA polymerase alpha-primase complex through chromatography on phosphocellulose and hydroxylapatite. Separation from DNA polymerase alpha-primase complex as well as from the bulk of another DNA-dependent ATPase was achieved on heparin-Sepharose. Further purification steps included ATP-agarose and fast protein liquid chromatography-Mono S. A 47-kDa polypeptide cosedimented with the DNA helicase activity in a glycerol gradient as well as in gel filtration on Superose 6. The calf thymus DNA helicase had a sedimentation coefficient of 4-7 S and Stokes radius of about 45 A suggesting that the enzyme might be monomer in its functional form. DNA helicase activity requires a divalent cation with Mg2+ being more efficient than Mn2+ or Ca2+. Hydrolysis of ATP is required since the two nonhydrolyzable ATP analogs adenosine 5'-O-(3-thiotriphosphate) and adenylyl (beta, gamma-methylene)diphosphonate cannot substitute for ATP or dATP in the displacement reaction. Calf thymus DNA helicase is able to use ATP, dATP, dideoxy-ATP, CTP, and dCTP with Km for ATP and dATP of 0.2 and 0.25 mM, respectively. The enzyme can displace a fragment of 24 bases completely in an enzyme concentration- and time-dependent manner. The DNA helicase appears to bind to single-stranded DNA and to move to single-strand double-strand transition. The directionality of unwinding is 3'----5' with respect to the single-stranded DNA to which the enzyme is bound.
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PMID:DNA helicase from calf thymus. Purification to apparent homogeneity and biochemical characterization of the enzyme. 197 96

Examination of retinal tissue homogenates indicated the presence of a [Ca2+ + Mg2+]-dependent adenosinetriphosphatase activity that exhibited high affinity for Ca2+ (K0.5 = 0.17 microM) and moderately high affinity for Mg2+ and ATP (K0.5 = 12.5 microM and Km = 22.8 microM, respectively). Maximum ATP hydrolysis occurred at pH 7.4. Under conditions of optimal substrate, cation and hydrogen ion concentrations, specific activity ranged from 15 to 18 nmol phosphate released min-1 mg-1 protein. Although the retinal [Ca2+ + Mg2+] adenosinetriphosphatase hydrolyzes both ATP and dATP, other nucleotides (CTP, GTP, ITP and UTP) were not hydrolyzed to any great extent. The monovalent cations, Li+, K+ and Na+, had no effect upon hydrolysis of ATP; whereas Cs+ and NH4+ ions were moderately (approximately 30%) inhibitory. All divalent cations tested were stimulatory. With the exception of rotenone which inhibited ATP hydrolysis approximately 25%; retinal adenosinetriphosphatase activity was insensitive to mitochondrial inhibitors (NaN3, KCN, ruthenium red and oligomycin). Adenosinetriphosphatase activity was observed to be very sensitive to low concentrations (I50 approximately 2 microM) of vanadate; whereas, lanthanum administration resulted in no inhibition. Removal of calmodulin (80%) resulted in reducing adenosinetriphosphatase activity 60% but addition of exogenous calmodulin back to calmodulin deficient membranes did not restore activity to starting levels. Calmodulin antagonists trifluoperazine and calmidazolium reduced significantly Ca2+ stimulated, Mg2+ dependent ATP hydrolysis. We conclude that the [Ca2+ + Mg2+]-dependent adenosinetriphosphatase of bovine retina is a non-mitochondrial protein exhibiting very high affinity for Ca2+ and appears to require calmodulin for maximum activity. Because of its high affinity for Ca2+, this protein may play an important role in reducing intracellular Ca2+ to nanomolar levels.
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PMID:Partial characterization of a high affinity [Ca2+ + Mg2+]-dependent adenosinetriphosphatase from bovine retina. 213 89

Polyoma virus large tumor antigen (PyV T antigen) has been purified to near homogeneity by immunoaffinity column chromatography. We have detected DNA helicase and ATPase (nucleoside-5'-triphosphatase) activities in the purified PyV T antigen fraction and characterized these activities. The ATPase activity was stimulated about 2-fold by poly(dT), which was the most effective stimulator among the synthetic polynucleotides tested. Natural nucleic acids, such as calf thymus native and heat-denatured DNA, and single-stranded circular fd DNA were also effective, but the degree of stimulation was less than 1.5-fold. The basal and poly(dT)-stimulated ATPase activities showed similar preference for nucleoside 5'-triphosphates, requirement for divalent cations, and pH optima. The preference for nucleoside 5'-triphosphates was ATP, dATP greater than CTP, UTP much greater than GTP. The only difference observed between the two activities was salt sensitivity. The basal ATPase activity was resistant to KC1 up to 300 mM. In contrast, poly-(dT)-stimulated activity was reduced to the level of basal activity at 300 mM KC1. DNA helicase activity required divalent cations and was dependent on hydrolysis of ATP. The activity showed similar preference for nucleoside 5'-triphosphates, requirement for divalent cations, and pH optimum as the two ATPase activities, and the salt sensitivity of DNA helicase activity was similar to that of poly(dT)-stimulated ATPase activity. The helicase activity was inhibited competitively by the addition of single-stranded or double-stranded DNA, and a relatively high inhibitory activity was observed with poly [d(A-T)]. The PyV T antigen helicase was found to migrate in the 3' to 5' direction along the DNA strand to which the protein bound.
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PMID:DNA helicase and nucleoside-5'-triphosphatase activities of polyoma virus large tumor antigen. 216 Feb 69

Approximately one-third of the total ATP-hydrolysis activity in isolated HeLa nuclei is sensitive to RNAase (ribonuclease). This activity is selectively extracted with pulse-labelled RNA. In the extracts it co-sediments with various particles with sedimentation coefficients from 10S to 50S, but especially with 24S and 40S particles. ATP hydrolysis by the isolated particles was inhibited extensively (greater than 80%) by RNAase A, heparin and 0.2 M-NaCl. The activity of RNAase-treated particles was recovered when poly(A) was added, but not when DNA was added. The isolated particles exhibited RNAase-sensitive hydrolysis activities for dATP, GTP, CTP and UTP as well as for ATP, and the UTPase activity in the extracts showed nearly the same sedimentation distribution as the ATPase activity. When samples of isolated particles were irradiated with u.v. light in the presence of [alpha-32P]ATP, a 39 kDa polypeptide with a broad distribution from 10S to 50S like that of the ATPase and a 55 kDa polypeptide with a sharp distribution at 24S were photolabelled. Taken together, the data suggest that ATP-hydrolysis activity found in nuclear ribonucleoprotein subfractions appears to be the result of one or two RNA-dependent NTPases that are normally associated with endogenous RNA in a wide variety of particles.
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PMID:Characterization of a ribonuclease-sensitive nucleoside triphosphatase activity from HeLa nuclei. 240 2

We have compared the ATPase, DNA-binding, and helicase activities of free simian virus 40 (SV40) large T antigen (To) and T antigen complexed with cellular p53 (T+p53). Each activity is essential for productive viral infection. The T+p53 and To fractions were prepared by sequential immunosorption of infected monkey cells with monoclonal antibodies specific for p53 and T antigen. The immune-complexed T fractions were then assayed in parallel. For ATP hydrolysis, the Vmax for T+p53 was 143 nmol of ADP per min per mg of protein, or 18-fold greater than for To. ATP had no effect on the stability of the T+p53 complex. The T+p53 complex was significantly more active than To in hydrolyzing dATP, dGTP, GTP, and UTP. Of the nucleotide substrates tested, the greatest relative increase (T+p53/To) was in hydrolyzing dGTP and GTP. In DNase footprinting assays performed under replication conditions, the T+p53 complex protected regions I, II, and III of origin DNA while equivalent amounts of To protected only regions I and II. Region III is known to contribute to the efficiency of DNA replication and contains the SP1-binding sites of the early viral promoter. The T+p53 fraction was also a more efficient helicase than To, especially with a GC-rich primer and template. Thus, the T+p53 complex has enhanced ATPase, GTPase, DNA-binding, and helicase activities. These findings imply that complex formation between cellular monkey p53 and SV40 T antigen modulates a number of essential activities of T in SV40 productive infection.
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PMID:The p53 complex from monkey cells modulates the biochemical activities of simian virus 40 large T antigen. 252 75

We show that MalT, the transcriptional activator of the Escherichia coli maltose regulon, specifically binds ATP and dATP with a high affinity (Kd = 0.4 microM) and exhibits a weak ATPase activity. Using an abortive initiation assay, we further show that activation of open complex formation by MalT depends on the presence of ATP in addition to that of maltotriose, the inducer of the maltose system. Similar experiments in which ATP was replaced by ADP or AMP-PNP, a non-hydrolysable analogue of ATP, demonstrate that this reaction does not require ATP hydrolysis. As revealed by DNase I footprinting, both ATP and maltotriose are required for the binding of the MalT protein to the mal promoter DNA.
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PMID:MalT, the regulatory protein of the Escherichia coli maltose system, is an ATP-dependent transcriptional activator. 252 84

The Ca2+-stimulated, Mg2+-dependent ATPase of SV40 transformed WI38 lung fibroblast homogenates exhibits a high affinity for Ca2+ (K0.5 = 0.20 microM) and moderately high affinity for ATP (Km = 28.6 microM) and Mg2+ (K0.5 = 138.5 microM). This activity was NaN3, KCN and oligomycin insensitive but very sensitive to vanadate (I50 = 0.5 microM) suggesting its being neither mitochondrial or microsomal but plasma membrane in origin. Under optimal conditions of protein, hydrogen ion and substrate concentration, 16-19 nmoles phosphate was released per min per mg protein. Hill plot analysis indicated no cooperativity to occur between Ca2+ binding sites. Nucleotides other than ATP and dATP were ineffective as substrates. The trivalent cation, lanthanum (La3+) completely inhibited hydrolysis of ATP at approximately 70 microM (I50 = 25 microM). Calmodulin antagonists trifluoperazine and calmidazolium inhibited ATP hydrolysis in a dose dependent fashion.
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PMID:The [Ca2+ + Mg2+]-dependent adenosine triphosphatase of SV40 transformed WI38 lung fibroblasts. 252 8


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