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)

Cells of Escherichia coli contain two nucleoside-transport systems. Energy-starved cells of a strain containing only one of these systems and, in addition, carrying a mutation in the Ca2+- and Mg2+-dependent ATPase (ATP phosphohydrolase 3.6.1.3) are still able to transport nucleosides. The rate is only slightly lower than the rate measured in unstarved cells. Freshly harvested uncA cells transport purine nucleosides at a higher rate than cells from the isogenic strain containing a functional ATPase. If cells from the latter strain are treated with arsenate, transport rates increase to the same levels as found in uncA cells. The presence of an uncA mutation has no effect on the transport rates for cytidine, deoxycytidine, and uridine, nor has arsenate treatment. These findings indicate that ATP is not required as energy donor for nucleoside transport. The enhanced transport rate for purine nucleosides after treatment with arsenate seems to suggest a regulatory relationship between the transport of these nucleosides and the cellular levels of ATP or a closely related metabolite.
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PMID:Stimulatory effect of low ATP pools on transport of purine nucleosides in cells of Escherichia coli. 644 15

Soluble human colon carcinoma extract(s) (SCE) were potent nonspecific inhibitors of lymphoproliferative responses to mitogens. Inhibition was concomitant with induction in about 35% of cells of morphologic alterations for most of them comparable with the ones observed in mitogen-induced blast cells. Nonetheless, these blastlike cells did not proliferate. SCE did not interfere with mitogen binding to cell receptors. Moreover, SCE was unable to induce or activate suppressor cells, and its primary target cell was the unresponsive lymphoid cell itself. The inhibitory effect of SCE was early and irreversible. The differential activity of SCE can be correlated with an early [3H]uridine uptake, which was inhibited 6 hours later, as seen for the other biochemical parameters of cell activation. Also, SCE altered membrane-bound ATPase activities. Na,K-ATPase was strongly inhibited, whereas Ca2+-dependent and Mg2+-dependent ATPases were stimulated. These observations were discussed as an SCE-lymphocyte plasma membrane interaction translated into differential signals to the intracellular metabolic pathways.
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PMID:Nonspecific inhibitory activity of soluble human colon carcinoma extracts: tentative mechanism of action. 645 70

Ecto-ATPase activity of Xenopus oocytes was studied by measuring the production of inorganic phosphate (Pi) from the breakdown of extracellular ATP. Enzyme activity involved Ca2+/Mg(2+)-dependent and Ca2+/Mg(2+)-independent dephosphorylation of ATP. Ca2+/Mg(2+)-dependent ecto-ATPase was active over a limited range of 0.01-1.0 mM ATP, while Ca2+/Mg(2+)-independent ATPase activity was active over a range of 0.1-30 mM ATP. Total enzyme activity was insensitive to changes in buffer pH (pH 7.0-9.0), but increased in a relatively linear manner with: (1) time of reaction (0-90 min), (2) number of cells (1-20 oocytes), and (3) temperature (10-37 degrees C). Ecto-ATPase activity was unaffected by ouabain (100 microM), sodium azide (100 microM), and oligomycin (5 micrograms/ml) (as inhibitors of endo-ATPases) and beta-glycerophosphate (10 mM) and p-nitrophenyl phosphate (10 mM) (as inhibitors of non-specific alkaline phosphatase). Total ecto-ATPase activity was reduced significantly in defolliculated oocytes, suggesting that the enzyme was located mainly on the enveloping follicle cell layer. The range order of preferential substrates was: ATP>GTP, ITP, UTP, CTP, TTP, 2-methylthioATP>ADP, 2-methylthioADP, AMP>>alpha, beta-methylene ATP, beta, gamma-methylene ATP, in the presence of divalent ions (where G is guanosine, I is inosine, U is uridine, C is cytidine and T is ribosylthymine). The P2-purinoceptor antagonist suramin [8-(3-benzamido-4-methylbenzamido)napthalene-1,3,5-trisul phonic acid), 100 microM] significantly inhibited total ecto-ATPase activity; this inhibition was competitive for the Ca2+/Mg(2+)-dependent enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characteristics of ecto-ATPase of Xenopus oocytes and the inhibitory actions of suramin on ATP breakdown. 892 22

Solute uptake into liver plasma membrane vesicles from either lean or obese Zucker rats was monitored. D-Glucose and L-leucine uptakes at physiological concentrations of the substrate were not different in lean and obese Zucker rats. In agreement with a previous report (Ruiz et al. (1991) Biochem. J. 280, 367-372) L-alanine uptake was significantly enhanced in those preparations from obese animals. Na(+)-coupled uridine transport was markedly enhanced also in obese rats. The effect was due to an increase in Vmax (5.5 +/- 0.6 vs. 2.1 +/- 0.2 pmol/mg protein per 3 s, P < 0.01) without any significant change in Km (11.0 +/- 2.8 vs. 9.0 +/- 2.7 microM for obese and lean rats, respectively). Na+,K(+)-ATPase activity was also higher in liver plasma membrane vesicles from rat liver and it correlated with a higher amount of alpha 1-subunit protein in both, plasma membrane vesicles and homogenates from obese rat livers. In summary, in the hypertrophic liver of obese Zucker rats a coordinate induction of several Na(+)-dependent transport systems occurs and, in order to sustain the metabolic pressure associated with this adaptation, a significant induction of the Na+,K(+)-ATPase expression is also found. These data also provide new evidence for regulation of the recently characterized Na(+)-dependent nucleoside transporter.
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PMID:Coordinate induction of Na(+)-dependent transport systems and Na+,K(+)-ATPase in the liver of obese Zucker rats. 798 9

The vertebrate corneal endothelium represents a unique model system for investigating many cellular aspects of wound repair within an organized tissue in situ. The tissue exists as a cell monolayer that resides upon its own natural basement membrane that can be prepared as a flat mount to observe the entire cell population. Thus, it readily avails itself to many cytological and immunocytochemical methods at both the light microscopic and ultrastructural levels. In addition, the tissue is easily explanted into organ culture where further investigations can be carried out. These techniques have enabled investigators to use many approaches to explore function and changes in response to injury. In vivo, the endothelium acts as a transport tissue to actively pump Na+ and bicarbonate ions from the corneal stroma into the aqueous humor to control corneal transparency. Physiological findings indicate that fluid diffuses back into the stroma, across the endothelium, and thus hydration is said to be controlled by a pump-leak mechanism. Ultrastructural investigations, some employing horseradish peroxidase and lanthanum, have established the morphological basis for this mechanism as apical focal junctions that are not the classical tight junctions and do not constitute a complete zona occludens. Along with these apical focal junctions are gap junctions that appear identical to their counterparts in other cell types. Cytochemical studies localized both Na+K(+)-ATPase and carbonic anhydrase, the main pump enzymes associated with corneal hydration, to the lateral plasma membranes. Corneal endothelial cells of noninjured tissue do not traverse the cell cycle and are considered to be in the "Go" phase of the cell cycle as determined by microfluorometric analysis with DNA binding dyes such as auramin O and pararosaniline-Feulgen. However, injury can initiate cell cycle transverse and histochemical and cytological methods have been used to understand the tissue's response. Classical histochemical studies revealed that increased staining was observed for metabolic (NADase and NADPase) and lysosomal enzymes in cells bordering the wound area. The use of radiolabelled agents has further lead to an understanding of the endothelial wound response. Autoradiographic analyses of 3H-actinomycin D incorporation indicated that injury initiates changes in chromatin leading to increased binding levels of the drug in cells surrounding the wound. This change suggests that those cells undergo heightened macromolecular synthesis and this was confirmed by examining 3H-uridine and 3H-thymidine incorporation. The major mechanism involved in corneal endothelial repair is cell migration. Cytochemical and immunocytochemical investigations have allowed investigators an opportunity to gain some insight into changes that occur during this cellular process.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Cytological and immunocytochemical approaches to the study of corneal endothelial wound repair. 805 65

Interactions between proteins and nucleic acids are important in the fundamental cellular processes that drive replication, recombination, dynamic alteration and repair of DNA, transcription and processing of RNA, synthesis of proteins, and regulation of enzyme activities. As part of an effort to develop a general, sensitive mass spectrometric strategy for the characterization of protein-nucleic acid interactions, we have used matrix-assisted laser desorption-ionization (MALDI) time-of-flight mass spectrometry to analyze protein-nucleic acid complexes that have been covalently crosslinked by ultraviolet (UV) light. In general, the application of MALDI mass spectrometric techniques to studies of UV-induced crosslinking of nucleoprotein complexes is demonstrated to be feasible. Specifically, MALDI mass analysis was used to determine the molecular weights of the phage T4 gene 32 protein (gp32) crosslinked to the oligonucleotide (dT)20, and the Escherichia coli transcription termination factor rho, photoaffinity labeled with 4-thio-uridine-diphosphate (4sUDP). The covalent gp32:(dT)20 complex is readily detected at a concentration of 1-2 microM in 1 microL of an unpurified solution of reactants that has been exposed to a single, 266 nm UV laser pulse. Mass spectrometric molecular weight determinations of the covalent rho:4sUDP complex add directness and specificity to the ATPase inactivation assay normally used to monitor the formation of 4sUDP photoaffinity labeled rho. It is found that successful MALDI mass spectrometry of protein-nucleic acid complexes is as critically dependent on the choice of solvents and additives as it is on the primary matrix compound.
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PMID:Direct observation of UV-crosslinked protein-nucleic acid complexes by matrix-assisted laser desorption ionization mass spectrometry. 832 69

1. Uridine and uridine monophosphate (UMP) are natriuretic and a vasopressor in intact rats. In deoxycorticosterone acetate (DOCA)-salt hypertensive rats metabolic clearance rate (MCR) of uridine is raised and basal plasma uridine diminished, suggesting that metabolism of uridine is linked to changes in extracellular space. 2. Plasma uridine concentration was raised in 38 patients with chronic renal failure compared with age- and sex-matched healthy controls (8.49 mumol/L, 4.37-13.74 mumol/L median, interquartile range, and 2.64 mumol/L 2.51-2.74 mumol/L, respectively, P < 0.001). Plasma uridine was significantly diminished after isotonic fluid removal by ultrafiltration (UF) from 7.25 mumol/L (3.7-11.08) to 5.07 mumol/L (3.3-8.3), P < 0.001, whereas concentration of marker solutes urea and creatinine remained unchanged. During haemodialysis (HD), plasma uridine fell significantly from its pre-HD level. 3. In an animal model of expanded extracellular space the one-kidney, one-clip rat, plasma uridine was significantly higher (20.56 +/- 1.19 mumol/L, P < 0.01) and MCR diminished (34.93 +/- 3.44 mL/kg per min, P < 0.01) compared with sham-operated animals (plasma uridine 12.14 +/- 1.07 and MCR 53.59 +/- 4.11 mL/kg per min). Uridine or UMP did not inhibit Na+, K(+)-ATPase in either of the two assay systems. 4. It was concluded that catabolism of uridine is reduced by extracellular expansion and probably increased by volume reduction by UF.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolism of uridine in expanded extracellular volume states. 839 45

We report on the variant phenotypic expression of mitochondrial genotypes in cultured skin fibroblasts and Epstein-Barr virus-transformed lymphocyte cultures from a patient with Pearson syndrome (McKusick no. 260560). Both cell types harbored a heteroplasmic population of normal and deleted mtDNA molecules. The deletion encompassed five tRNA genes and seven genes encoding subunits of cytochrome c oxidase, complex I, and ATPase. Patient skin fibroblasts and lymphocytes harbored 60 and 80% of deleted mtDNA molecules, respectively, and initially displayed defective respiratory chain activities. In both cases, there was a progressive recovery of respiratory chain activities during in vitro cell proliferation. In cultured skin fibroblasts, the loss of the deleted mtDNA molecules accounted for the recovery of normal respiratory chain activities. These features were prevented by allowing respiratory chain-deficient cells to grow in the presence of uridine (200 microM). In Epstein-Barr virus-transformed lymphocytes containing 60% of deleted mtDNA, the recovery of respiratory chain activities was attributable to an increase in the mtRNA translation efficiency rather than to an increased content in mtDNA or mtRNA. The present study suggests that the variant cellular responses to abnormal mitochondrial genotypes might contribute to the tissue-specific expression of mitochondrial disorders in vivo.
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PMID:Fate and expression of the deleted mitochondrial DNA differ between human heteroplasmic skin fibroblast and Epstein-Barr virus-transformed lymphocyte cultures. 839 36

The [Ca2+ + Mg2+]-ATPase activity of bovine lactating mammary gland is associated with membranes. This study compares the ATPase activity in microsomal membranes to that of the Golgi apparatus. The enzyme activity in both fractions hydrolyzed Ca(2+)-ATP and Mg(2+)-ATP. The ATPase activities were inhibited by p-chloromercuribenzoate, indicating the involvement of a sulfhydryl group for activity. Although calmodulin had no effect on the ATPase activities of the two fractions, calmodulin antagonists (chlorpromazine, fluphenazine, and trifluoperazine) were inhibitory. Strong inhibitors of the ATPase activities were vanadate, dicyclohexyl-carbodiimide, La3+, and Zn2+. There were some differences in the activities from two membrane fractions. Although both fractions could hydrolyze all of the triphosphonucleotides, cytidine-5'-triphosphate and uridine-5'-triphosphate were poor substrates for the Golgi enzyme. Detergents diminished the activity of the microsomal enzyme to a much greater extent than the ATPase of the Golgi apparatus. Thus, the intact membrane may be more critical to microsomal activity. The role of these enzymes in Ca2+ accumulation in milk is discussed.
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PMID:Properties of [Ca2+ + Mg2+]-adenosine triphosphatases in the Golgi apparatus and microsomes of the lactating mammary glands of cows. 844 92

Deflection of the mechanically sensitive hair bundle atop a hair cell opens transduction channels, some of which subsequently reclose during a Ca2+-dependent adaptation process. Myosin I in the hair bundle is thought to mediate this adaptation; in the bullfrog's hair cell, the relevant isozyme may be the 119-kDa amphibian myosin I beta. Because this molecule resembles other forms of myosin I, we hypothesized that calmodulin, a cytoplasmic receptor for Ca2+, regulates the ATPase activity of myosin. We identified an approximately 120-kDa calmodulin-binding protein that shares with hair-bundle myosin I the properties of being photolabeled by vanadate-trapped uridine nucleotides and immunoreactive with a monoclonal antibody raised against mammalian myosin I beta. To investigate the possibility that calmodulin mediates Ca2+-dependent adaptation, we inhibited calmodulin action and measured the results with two distinct assays. Calmodulin antagonists increased photolabeling of hair-bundle myosin I by nucleotides. In addition, when introduced into hair cells through recording electrodes, calmodulin antagonists abolished adaptation to sustained mechanical stimuli. Our evidence indicates that calmodulin binds to and controls the activity of hair-bundle myosin I, the putative adaptation motor.
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PMID:Calmodulin controls adaptation of mechanoelectrical transduction by hair cells of the bullfrog's sacculus. 870 Sep 9


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