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)

The biological activity of 2,4,8-trichlorodibenzofuran (2,4,8-TCDF) was tested using 2 endpoints: (a) the promotion of enzyme-altered, preneoplastic foci initiated by diethylnitrosamine (DEN) in livers of weanling female Sprague-Dawley rats; and (b) the induction of aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH), a marker for cytochrome P-4501 activity, in livers of adult female Sprague-Dawley rats and in H4IIEC3 rat hepatoma cells. When animals were treated with 200 or 500 mg/kg 2,4,8-TCDF 5 X weekly over 10 weeks after a single application of 10 mg/kg DNA, the higher dose of 2,4,8-TCDF had a promoting effect on the appearance of preneoplastic foci. Thus number and total area of foci deficient in adenosine-5'-triphosphatase were significantly increased by a factor of 1.6. 2,4,8-TCDF induced AHH-activities in 9000 X g supernatants of liver 2-3-fold, when rats were treated with 100-1000 mg/kg/day for 5 days and monooxygenase activities determined after another 3 days. The amounts of 2,4,8-TCDF required for inducing AHH activity in H4IIEC3 cells were 7 orders of magnitude higher than those of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). the results indicate that the 2,4,8-TCDF has a biological activity which is extremely low compared to that of 2,3,7,8-TCDD.
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PMID:Biological activity of 2,4,8-trichlorodibenzofuran: promotion of rat liver foci and induction of cytochrome P-450-dependent monooxygenases. 263 Dec 93

The effects of thyroid hormone on nuclear-encoded mitochondrial inner membrane proteins were investigated by in vitro translation of the endogenous mRNA present in a postmitochondrial fraction from the livers of rats treated in vivo with hormone. The levels of the mRNAs were estimated by quantitative immunoabsorption of the translation mixture. Total protein synthesis was increased 2.6-fold after 4 days of in vivo hormone treatment, but only 10-15% of the polypeptides were dramatically altered (greater than 5-fold). Among the most highly elevated were cytochrome c1 (greater than 10-fold increase) and the Rieske iron-sulfur protein of the cytochrome bc1 complex. Other inner membrane proteins (core protein 1, beta subunit of F1 ATPase, subunit IV of cytochrome oxidase, 3-hydroxybutyrate dehydrogenase) and non-mitochondrial proteins (rat serum albumin, beta 2-microglobulin) were not altered significantly by hormone treatment. Cytochrome c1 and the Rieske protein increased after 12 h of hormone treatment, a relatively early response in mammalian mitochondrial biogenesis. The possible significance of this response for the regulation of mitochondrial synthesis and assembly is discussed.
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PMID:Thyroid hormone regulation of nuclear-encoded mitochondrial inner membrane polypeptides of the liver. 277 68

Three mutant strains of Bacillus subtilis were isolated on the basis of their ability to grow in the presence of 5 microM carbonyl cyanide m-chlorophenylhydrazone (CCCP). The mutants (AG2A, AG1A3, and AG3A) were also resistant to 2,4-dinitrophenol, and AG2A exhibited resistance to tributyltin and neomycin. The mutants all exhibited (i) elevated levels of membrane ATPase activity relative to the wild type; (ii) slightly elevated respiratory rates, with the cytochrome contents of the membranes being the same as or slightly lower than those of the wild type; (3) a passive membrane permeability to protons that was indistinguishable from that of the wild type in the absence of CCCP and that was increased by addition of CCCP to the same extent as observed with the wild type; and (4) an enhanced sensitivity to valinomycin with respect to the ability of the ionophore to reduce the transmembrane electrical potential. Finally and importantly, starved whole cells of all the mutants synthesized more ATP than the wild type did upon energization in the presence of any one of several agents that lowered the proton motive force. Studies of revertants indicated that the phenotype resulted from a single mutation. Since a mutation in the coupling membrane might produce such pleiotropic effects, an analysis of the membrane lipids was undertaken with preparations made from cells grown in the absence of CCCP. The membrane lipids of the uncoupler-resistant strains differed from those of the wild type in having reduced amounts of monounsaturated C16 fatty acids and increased ratios of iso/anteiso branches on the C15 fatty acids. Correlations between protonophore resistance and the membrane lipid compositions of the wild type, mutants, and revertants were most consistent with the hypothesis that a reduction in the content of monounsaturated C16 fatty acids in the membrane phospholipids is related, perhaps casually, to the ability to synthesize ATP at low bulk transmembrane electrochemical gradients of protons.
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PMID:Isolation and characterization of uncoupler-resistant mutants of Bacillus subtilis. 282 Sep 27

LM fibroblasts grown in a chemically-defined, serum-free medium readily incorporated choline or one of three analogues of choline, namely N,N-dimethylethanolamine, N-monomethylethanolamine, or ethanolamine into membrane phospholipids. The effect of these phospholipid manipulations in vitro on tumor growth and metastasis was examined in nude mice. Serum and choline-fed cells most frequently metastasized (74% and 68%, respectively), while frequency of lung metastasis was 46%, 42% and 17% in mice injected with cells fed with dimethylethanolamine, monomethylethanolamine, and ethanolamine, respectively. Metastases from cells cultured with serum, choline or dimethylethanolamine, but not from monomethylethanolamine or ethanolamine, were extensive and highly invasive. The specific activity of the (Na+ + K+)-ATPase but not of 5'-nucleotidase was significantly decreased in local tumor plasma membranes from choline analogue-fed cells as compared to tumor plasma membranes from choline-fed cells. When compared to the choline-fed tumor cells, the specific activities of three mitochondrial enzymes, namely NADH dependent, rotenone insensitive NADH-dependent, and rotenone sensitive NADH-dependent cytochrome-c reductase, were significantly increased in the choline analogue-supplemented cells. The arachidonic acid content of phosphatidylcholine in plasma membranes, microsomes, and mitochondria was significantly decreased in tumor membranes from choline analogue-fed cells as compared to tumor membranes from choline-fed cells. As compared to local tumor plasma membranes, the lung metastasis plasma membranes had elevated (Na+ + K+)-ATPase specific activity, phospholipid oleic and arachidonic acid content, and fluidity. In contrast, the 5'-nucleotidase specific activity, the content of cholesterol, phospholipid, and phosphatidylethanolamine were decreased in lung metastasis plasma membranes. In summary, membrane alterations of LM tumor cells in vitro (1) were not completely reversed in vivo, and (2) affected metastatic ability.
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PMID:Local and metastatic tumor growth and membrane properties of LM fibroblasts in athymic (nude) mice. 283 81

Translocational intermediates of precursor proteins of ATPase F1 beta subunit and cytochrome c1 across mitochondrial membranes were analyzed using two different approaches, transport at low temperature and transport after binding of precursor proteins to antibodies. Under both conditions precursors were partially transported into mitochondria in an energy-dependent manner. They were processed by the metalloprotease in the matrix but a major proportion of the polypeptide chains was still present at the outer face of the outer mitochondrial membrane. We conclude that transfer of precursors into the inner membrane or matrix space occurs through "translocation contact sites"; precursor polypeptides to F1 beta and cytochrome c1 enter the matrix space with the amino terminus first; and a membrane potential is required for the transmembrane movement on an amino-terminal "domain-like" structure but not for completing translocation of the major part of the polypeptides.
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PMID:Transport of proteins into mitochondria: translocational intermediates spanning contact sites between outer and inner membranes. 286 45

Several inner membrane proteins from rat liver mitochondria have been translated for the first time in rabbit reticulocyte lysates. These include the Rieske iron-sulfur protein, cytochrome c1 and core protein I of the cytochrome bc1 complex, the alpha and beta subunits of F1 ATPase, and subunit IV of cytochrome oxidase. All were translated from free polysomes as larger-molecular-mass precursors, and were processed to their mature forms by isolated liver mitochondria or by the isolated mitochondrial matrix fraction. In vitro processing, catalyzed by the isolated matrix fraction, is inhibited by rhodamine 6G. The latter is a fluorescent probe, which accumulates specifically in mitochondria of whole cells and which is used extensively to visualize mitochondrial morphology. The concentration of rhodamine 6G required for inhibition in vitro is similar to that of o-phenanthroline. Rhodamine 6G inhibits matrix-catalyzed processing of all precursors tested, indicating that the mechanism of inhibition is common for a variety of functionally unrelated precursors. The novel action of rhodamine 6G reported here can form the basis for its inhibition of precursor processing in intact hepatoma cells [Kolarov, J. & Nelson, B.D. (1984) Eur. J. Biochem. 144, 387-392].
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PMID:Rhodamine 6G inhibits the matrix-catalyzed processing of precursors of rat-liver mitochondrial proteins. 286 95

It is possible to prepare liposomal vesicles by solubilization of total bacterial membranes with n-heptyl beta-D-thioglucoside followed by reconstitution into proteoliposomes by a freeze-thaw-sonication procedure with soybean phospholipids. The resulting proteoliposomes from total membrane fraction of sufficiently aerated cells of the thermophilic bacterium PS3 containing cytochrome aa3 showed a reasonable H+ pumping activity upon addition of reduced cytochrome c. On the other hand, the proteoliposomes reconstituted from air-limited PS3 cells containing cytochrome o and those from Nitrobacter agilis cells containing cytochrome aa3 did not show H+ pumping upon addition of reduced cytochrome c, although the vesicles showed "respiratory control"; 3-4-fold stimulation of oxygen consumption took place upon addition of an uncoupler. In proteoliposomes prepared from PS3 membranes by this method, H+-translocating ATPase (F0 X F1) was successfully reconstituted as well, suggesting that this method has wide applicability for investigation of enzymes catalyzing transmembrane processes.
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PMID:Measurement of proton pump activity of the thermophilic bacterium PS3 and Nitrobacter agilis at the cytochrome oxidase level using total membrane and heptyl thioglucoside. 288 79

We have made use of a panel of mouse-hamster somatic cell hybrids and restriction fragment length polymorphisms between two mouse species (Mus musculus and Mus spretus) to determine the chromosomal localization of genes encoding the alpha and beta subunits of the Na,K-ATPase (Na+,K+-activated ATP phosphohydrolase, EC 3.6.1.3). DNA probes for three distinct isoforms of the Na,K-ATPase alpha subunit mapped to three different mouse chromosomes: the alpha 1 gene (Atpa-1) cosegregated with the Egf gene on chromosome 3; alpha 2 (Atpa-2) with the cytochrome P-450PB gene family/coumarin hydroxylase locus on chromosome 7; alpha 3 (Atpa-3) with the alpha-spectrin gene on chromosome 1. The Na,K-ATPase beta-subunit gene (Atpb) mapped to the same region of chromosome 1, but it was not tightly linked to the Atpa-3 gene. These results indicate that three isoforms of the Na,K-ATPase alpha subunit are encoded by three distinct genes. The dispersion of Na,K-ATPase genes suggests that their expression is not likely to be controlled by a common cis-acting regulatory element.
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PMID:Genes encoding alpha and beta subunits of Na,K-ATPase are located on three different chromosomes in the mouse. 288 48

During reconstitution of pig heart mitochondrial H(+)-ATPase in soybean phospholipid liposomes by the cholate dialysis method, Mg2+ greatly enhanced 32Pi-ATP exchange activity, ATPase activity and the sensitivity to oligomycin or DCCD of the reconstituted enzyme complex. The effect of Mg2+ on the lipid packing or fluidity of the reconstituted proteoliposomes was measured by means of spin labels, fluorescent probes and pyrene excimer formation efficiency. A difference in fluidity seemed to be localized near the polar faces of lipid bilayers of the reconstituted enzyme complex. Fluidity was less in the presence of Mg2(+)-containing and the Mg2(+)-'free' samples. Based on the results obtained a hypothetical scheme was proposed for Mg2(+)-mediated change in the physical state of phospholipid modulates incorporating H(+)-ATPase in liposomes. It postulated that Mg2+ may play a role in altering the lipid fluidity of the bilayers, which would induce a change of conformation of F0 portion (buried in the lipid core) of H(+)-ATPase complex. Such change could be transmitted to the soluble F1 portion, the conformation of which is in turn altered, resulting in higher enzymatic activity. Such an assumption was further supported by the results of a series of biochemical and biophysical experiments. Similar to its effect in the reconstitution of porcine heart mitochondrial H(+)-ATPase in liposomes, Mg2+ may also enhance the enzyme activity of reconstituted cytochrome C oxidase, porcine kidney medulla Na,K-ATPase, Ca-ATPase from rabbit sarcoplasmic reticulum and chloroplast H(+)-ATPase, in liposomes. It may be inferred that the structure and function of many membrane proteins are similarly modulated by Mg2+.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Magnesium mediated change in physical state of phospholipid modulates membrane ATPase activity. 290 61

The effect of a single dose of 5 mg/kg body weight of aflatoxin B1 on rat liver mitochondrial enzymes, succinate dehydrogenase (SDH) and Mg++ adenosine triphosphatase (Mg++-ATPase) and on certain lipids were studies at various intervals of time from 3 to 24 hours. A significant decrease in the specific activity of SDH was observed after 6, 12, 18 and 24 hr treatment. The Mg++-ATPase activity remained unaffected up to 12 hr but appreciably decreased after, 18 and 24 hr of the treatment. The level of phospholipids and cholesterol were not altered after 3, 6 and 12 hr treatment, thereafter (18 and 24 hr) an increase was observed in both the lipids following the aflatoxin treatment. Medroxyprogesterone acetate (MPA) did not cause any alteration in the specific activities of these enzymes as well as levels of cholesterol and phospholipids. The treatment with MPA caused significant increase in contents of cytochromes P-450, b5 and activities of Arylhydrocarbon hydroxylase (AHH), UDP-glucuronyl transferase (UDP-GT) and NADPH-cytochrome C-reductase of hepatic microsomes. It was observed that pretreatment with medroxyprogesterone acetate (MPA) could significantly minimuze the depression caused in mitochondrial SDH and Mg++-ATPase activities by aflatoxin B1.
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PMID:Modification of aflatoxin B1-induced changes in certain mitochondrial enzymes and lipids by medroxyprogesterone acetate. 294 74


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