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)

Studies of neutrophil nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation in a cell-free system showed that the low molecular-weight guanosine triphosphatase (GTPase) Rac was required, and that Rap1a may participate in activation of the catalytic complex. Full-length posttranslationally modified Rac2 was active, whereas only the 1-166 truncated form of Rap1a was functional in the cell-free system, and thus, clarification of the function of Rap1a and Rac2 in intact human phagocytes is needed to provide further insight into their roles as signal transducers from plasma membrane receptors. In the present studies, oligonucleotide-directed mutagenesis was used to introduce a series of mutations into human rap1a or rac2 in the mammalian expression vector pSR alpha neo. HL60 cells transfected with wild-type or mutated rac2 or rap1a cDNA constructs and control HL60 cells transfected with the pSR alpha neo vector containing no inserted cDNA were selected in G418-containing media, then subclones were isolated. Compared with the parent HL60 cells, each of the stable transfected cell lines differentiated similarly into neutrophil-like cells and expressed comparable levels of NADPH oxidase components p47-phox, p67-phox and gp91-phox. The differentiated vector control cell line produced O2. in response to receptor stimulation at rates that were not significantly different from parent HL60 cells. O2-. production by differentiated cell lines expressing mutated N17 Rap1a or N17 Rac2 dominant-negative proteins was inhibited, whereas O2-. production by the subline overexpressing wild-type Rap1a was increased by fourfold. O2-. production by the differentiated cell line expressing GTPase-defective V12 Rap1a was also significantly inhibited, a finding that is consistent with a requirement for cycling between guanosine diphosphate- and GTP-bound forms of Rap1a for continuous NADPH oxidase activation in intact neutrophils. A model is proposed in which Rac2 mediates assembly of the p47 and p67 oxidase components on the cytosolic face of the plasma membrane via cytoskeletal reorganization, whereas Rap1a functions downstream as the final activation switch involving direct physical interaction with the transmembrane flavocytochrome component of the NADPH oxidase.
...
PMID:Function of wild-type or mutant Rac2 and Rap1a GTPases in differentiated HL60 cell NADPH oxidase activation. 783 80

The enhancer-binding protein NIFA is required for transcriptional activation of nif promoters by the alternative holoenzyme form of RNA polymerase, which contains the sigma factor sigma 54 (sigma N). NIFA hydrolyzes nucleoside triphosphates to catalyze the isomerization of closed promoter complexes to transcriptionally competent open complexes. The activity of NIFA is antagonized by the regulatory protein NIFL in response to oxygen and fixed nitrogen in vivo. We have investigated the requirement for nucleotides in the formation and stability of open promoter complexes by NIFA and inhibition of its activity by NIFL at the Klebsiella pneumoniae nifH promoter. Open complexes formed by sigma 54-containing RNA polymerase are considerably more stable to heparin challenge in the presence of GTP than in the presence of ATP. This differential stability is most probably a consequence of GTP being the initiating nucleotide at this promoter. Adenosine nucleosides are specifically required for Azotobacter vinelandii NIFL to inhibit open complex formation by native NIFA, and the nucleoside triphosphatase activity of NIFA is strongly inhibited by NIFL under these conditions. We propose a model in which NIFL modulates the activity of NIFA via an adenosine nucleotide switch.
...
PMID:Transcriptional activation of the nitrogenase promoter in vitro: adenosine nucleotides are required for inhibition of NIFA activity by NIFL. 786 90

Oxytocin stimulates phosphoinositide turnover in myometrium. To elucidate whether the coupling mechanism involves the interaction of oxytocin receptor with GTP-binding proteins, we examined oxytocin stimulation of guanosine triphosphatase (GTPase) activity and phospholipase-C activity in rat and human myometrial membranes. Oxytocin consistently stimulated both GTPase and phospholipase-C activities, and both stimulations were attenuated by an antibody directed against the carboxyl-terminals of the GTP-binding proteins, G alpha q and G alpha 11. Neutralization of the antibody by preincubation with antigenic peptide reversed this inhibition. [Thr4,Gly7]oxytocin, a specific oxytocin receptor agonist, stimulated both GTPase and phospholipase-C activities, and the stimulations were also inhibited by anti-G alpha q/11 IgG. Immunoreactive GTP-binding proteins, G alpha q and G alpha 11, and phospholipase-C beta 3 isoforms were present in myometrial membranes. These results indicate that stimulation of phospholipase-C activity by oxytocin in myometrium is mediated via G alpha q, G alpha 11, or a closely related GTP-binding protein, probably coupling to phospholipase-C beta.
...
PMID:Oxytocin stimulates myometrial guanosine triphosphatase and phospholipase-C activities via coupling to G alpha q/11. 789 60

A Ca(2+)- or Mg(2+)-stimulated ecto-ATPase is thought to regulate the hydrolysis of extracellular ATP in nervous tissues. The hydrolysis of nucleotide triphosphates (NTPs) was analyzed in brain microsomal fractions from crosses of DBA/2J (D2) and C57BL/6J (B6) mice. The nucleotide triphosphatase (NTPase) activity was significantly reduced in D2 mice as compared to B6 mice, and B6D2F1 hybrids had activities intermediate to the parentals. A significant positive correlation was found between the hydrolysis of four NTPs (ATP, CTP, GTP and UTP) in 24 B6 x D2 (BXD) recombinant inbred (RI) strains of mice and in 80 B6D2F1 x D2 backcross mice. The RI strains and backcross mice fell into two distinct groups with respect to the NTPase activity. Linkage of NTPase activity was suggested with the chromosome 2 markers, D2Mit6 and Ass-1, in the RI strains, and was confirmed by analysis of other markers in the backcross population. These data suggest that the Ca(2+)- or Mg(2+)-stimulated hydrolysis of NTPs, designated Ntp, is regulated by a single gene located on proximal chromosome 2. Although an association was observed previously between Ca(2+)-ATPase activity and susceptibility to audiogenic seizures (AGS), no significant association was observed for the expression of Ntp and AGS susceptibility.
...
PMID:Genetic analysis of nucleotide triphosphatase activity in the mouse brain. 805 15

1. Parotid plasma membrane nonpump low-affinity Ca(2+)-ATPase, which possesses high-affinity (Ca2+ + Mg2+)-ATPase activity, was characterized. 2. Purified Ca(2+)-ATPase hydrolyzed the nucleoside triphosphates, GTP, ITP, CTP, UTP, TTP (67-93% of ATP) and nucleoside diphosphates, ADP, GDP, IDP, CDP, TDP (12-40% of ATP) but not AMP and p-NPP. 3. The maximum activities of Ca(2+)- and (Ca2+ + Mg2+)-ATPases were obtained in the presence of 1 mM and 0.13 microM Ca2+, respectively. 4. The Km values for Ca2+ in Ca(2+)- and (Ca2+ + Mg2+)-ATPases were 0.2 mM and 22 nM, respectively. 5. The activities of both Ca(2+)- and (Ca2+ + Mg2+)-ATPases were found in the right-side-out-vesicles obtained from the plasma membrane-rich fraction. 6. These features suggest that Ca(2+)-ATPase is an ecto-Ca(2+)-dependent nucleoside triphosphatase.
...
PMID:The possibility that Ca(2+)-ATPase from the plasma membrane-rich fraction of bovine parotid gland is ecto-Ca(2+)-dependent nucleoside triphosphatase. 806 15

The relationship between ecto-ATPase activity and the vasoactive effect of ATP is unclear. Previously we have characterized the ectonucleoside triphosphatase activity of isolated rat mesenteric small arteries and now characterize the effect of nucleotides on the tone of these arteries. In resting arteries, ATP caused concentration-dependent contractions that were transient and could not be reproduced within 2 h. Transient contractions in response to ATP also were elicited in arteries precontracted with norepinephrine, but the potency of ATP was increased and responses to repeated stimulations could be obtained. Contractions were followed by relaxation. The response to ATP was unaffected by 100 microM theophylline, 1 microM propranolol or removal of the endothelium. Transient contractions followed by relaxation were caused also by ADP, 2-methyl-thio-ATP (2meSATP) and alpha, beta-methylene-ATP (alpha, beta-meATP). UTP caused sustained contractions, whereas GTP and ITP had little effect. The rank order of potency (alpha, beta-,mATP > ATP > ADP) suggested that P2x purinoceptors were responsible for the contractions, whereas the rank order of potency for the relaxation (alpha, beta-meATP > or = ATP > 2meSATP) was not consistent with the relaxation being mediated by P2Y purinoceptors as defined originally. Desensitization of the contractile response to ATP by alpha, beta-meATP was variable. In contrast, inhibition of the response to ATP was obtained consistently and dose-dependently with GTP.
...
PMID:Effects of ATP and related nucleotides on the tone of isolated rat mesenteric resistance arteries. 845 Apr 60

The nuclear import factor p10 was cloned from Saccharomyces cerevisiae and found to be essential. The protein p10 can bind directly to several peptide repeat-containing nucleoporins. It also binds to the guanosine triphosphatase (GTPase) Ran in its guanosine diphosphate (GDP)-bound form and to karyopherin beta. Assembly of the karyopherin heterodimer on immobilized nucleoporin yielded cooperative binding of p10 and Ran-GDP. Addition of GTP to this pentameric complex led to dissociation of karyopherin (chi, presumably via in situ formation of Ran-GTP from Ran-GDP. Thus, p10 appears to coordinate the Ran-dependent association and dissociation reactions underlying nuclear import.
...
PMID:Role of the nuclear transport factor p10 in nuclear import. 860 May 22

We have described a thyroid hormone receptor in synaptosomes of the chick embryo brain. To understand how the hormones exert their actions at this level, we performed a series of studies to demonstrate that this receptor could be linked to G proteins. Guanosine 5'-[gamma-thio]triphosphate (GTP gamma S)(100 muM) lowered the binding capacity of the receptor high affinity site from 8.9 +/- 1.3 to 3.4 +/- 1.3 ng T3/mg protein, a finding consistent with the coupling of receptor to G proteins. Furthermore, ADP ribosylation with pertussis toxin showed that thyroid hormones induced a dose-dependent increase in the inactive alpha 0-subunit of the G0 protein. This effect was detected at 10 pM, with a maximal increase (mean +/- SEM, 50 +/- 3.6%) at 100 nM, and T4 was as effective as T3. Both hormones also decreased the intrinsic guanine triphosphatase activity of G proteins by lowering the binding of GTP to the alpha-subunit and their rate of hydrolysis. This inhibition was greater with T4 (25 +/- 5%) than with T3 (14 +/- 2%), suggesting that the former could be the more active hormone at the synaptosomal level. The effect on guanine triphosphatase activity confirms that the synaptosomal thyroid hormone receptor is coupled to a G(zero) protein. These results demonstrate that thyroid hormones increase or favor the ADP ribosylation of G alpha(zero) by pertussis toxin. Thus, they enhance the alpha(zero)-GDP form of the G(zero) protein, namely its inactive conformation. By decreasing the activity of this protein, these hormones may modulate the formation of second messengers in synaptosomes and intervene in the regulation of neuronal proliferation and differentiation induced by several factors. Therefore, thyroid hormones may exert their action on brain maturation at least in part by modulating G alpha(zero) through their synaptosomal receptor.
...
PMID:Effect of thyroid hormones on G proteins in synaptosomes of chick embryo. 864 Dec 9

A nuclear pore complex-associated nucleoside triphosphatase (NTPase) activity is believed to provide energy for nuclear export of poly(A)+ mRNA. This study was initiated to determine if nuclear membrane lipid composition is altered during chronic hyperlipidemia, and what effect this has on NTPase activity. The JCR:LA-cp corpulent rat model is characterized by severe hypertriglyceridemia and moderate hypercholesterolemia, and thus represents an ideal animal model in which to study nuclear cholesterol and NTPase activity. NTPase activity was markedly increased in purified hepatic nuclei from corpulent female JCR:LA-cp rats in comparison to lean control rats as a function of assay time, [GTP], [ATP], and [Mg2+]. Nuclear membrane cholesterol and phospholipid content were significantly elevated in the corpulent animals. Nuclei of corpulent animals were less resistant to salt-induced lysis than nuclei of lean animals, suggesting a change in relative membrane integrity. Together, these results indicate that altered lipid metabolism in a genetic corpulent animal model can lead to changes in nuclear membrane lipid composition, which in turn may alter nuclear membrane NTPase activity and integrity.
...
PMID:Nuclear cholesterol content and nucleoside triphosphatase activity are altered in the JCR:LA-cp corpulent rat. 891 86

We have isolated an ADP-ribosylation factor (ARF) gene from the human malarial parasite, Plasmodium falciparum. The gene (P. falciparum arf1) has four introns and the exons encode a protein of 181 amino acids with high similarity to the mammalian class I ARF proteins 1-3 (> or = 74% amino acid identity). Southern hybridization suggests there is at least one additional arf in the P. falciparum genome. Northern analysis identified a single P. falciparum arf1 mRNA of 1.8 kb in the asexual blood stage form of the parasite. The P. falciparum arf1 mRNA levels are developmentally regulated, reaching a maximum during nuclear division towards the end of the intraerythrocytic cycle. P. falciparum arf1 cDNA was isolated by reverse-transcriptase polymerase chain reaction and used to express a recombinant protein in Escherichia coli. Recombinant P. falciparum ARF1 protein was purified with stoichiometric amounts of bound GDP, although intrinsic guanose triphosphatase activity of the protein could not be detected. The protein stimulated cholera-toxin-catalyzed ADP-ribosyltransferase activity in a reaction that was dependent upon the addition of both dimyristoylglycerophosphocholine and cholate. The protein bound GTP with first-order kinetics with an apparent rate constant, k', of 0.0145 (+/- 0.0019) min-1. These results suggest that P. falciparum ARF1 is a member of the class 1 ARF family and provide additional evidence for the existence of a classical secretory pathway in P. falciparum.
...
PMID:Isolation, expression and characterization of the gene for an ADP-ribosylation factor from the human malaria parasite, Plasmodium falciparum. 895 60


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

---