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)

Resonance Raman (RR) spectra are reported for reduced submitochondrial particles (SMP) with excitation at 441.6 nm, where Raman bands of the cytochrome c oxidase heme a groups are selectively enhanced. Addition of ATP to energize the membranes induces the formation of a new band at 1644 cm-1 and partial loss of intensity in a band at 1567 cm-1. These changes are modeled by adding cyanide to reduced cytochrome c oxidase and are attributed to partial conversion of cytochrome (cyt) a3 from a high-spin to a low-spin state. This conversion is abolished by addition of excess oligomycin, an ATPase inhibitor, or FCCP, an uncoupler of proton translocation, and is reversed when the ATP is consumed. The observed spin-state conversion is attributed to the binding of an endogenous ligand to the cyt a3 Fe atom. This ligation is suggested to be induced by a local increase in pH and/or by a global conformation change associated with the generation of a transmembrane potential. Since O2 binding requires a vacant coordination site at cyt a3, the ligation of this site must retard O2 reduction and could thus provide a simple mechanism for energy-linked regulation of respiration. No changes in the RR spectrum were observed upon adding Ca2+ or H+ to reduced cytochrome c oxidase. The cyt a3 spin-state change associated with membrane energization is unrelated to the cyt a absorption red shift induced by adding Ca2+ or H+ to cytochrome c oxidase.
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PMID:Resonance Raman evidence for low-spin Fe2+ heme a3 in energized cytochrome c oxidase: implications for the inhibition of O2 reduction. 215 29

The single nuclear gene encoding human ubiquinone-binding protein, a subunit of the cytochrome bc1 complex, was isolated previously (Suzuki, H., Hosokawa, Y., Toda, H., Nishikimi, M., and Ozawa, T. (1989) Biochem. Biophys. Res. Commun. 161, 371-378). The 5'-flanking region contains four putative CCAAT boxes, one putative NF-Y-binding site, and one sequence homologous to the AP-1 recognition site, but lacks typical TATA and GC boxes. Three common nucleotide sequences (5'-TATTCAGGT-3', 5'-ATCTGGCT-3', and 5'-TGGTGA(T/G)AG-3', designated Mt1, Mt3, and Mt4, respectively) were found in the 5'-flanking regions of the genes for human ubiquinone-binding protein and for human cytochrome c1, another subunit of the cytochrome bc1 complex. All three sequences are located in the 280-base pair BamHI-HindIII fragment of the ubiquinone-binding protein gene and in the 154-base pair SalI-PstI fragment of the cytochrome c1 gene. Interestingly, a computer-assisted homology search revealed that the SalI-PstI fragment of the cytochrome c1 gene is related to the long terminal repeat of an endogenous retrovirus. Sequences highly homologous to the three Mt-sequences were also found in the 5'-flanking regions of the genes for the beta subunit of human F0F1-ATPase and rat somatic cytochrome c. The Mt1 sequence (TATT-CAGGT) is similar to the GFII recognition site (RTCACGTG) found in the 5'-flanking regions of the yeast nuclear genes for three cytochrome bc1 complex subunits. Gel retardation assay demonstrated that protein factors in a whole HeLa cell extract bound to both of those fragments. At least three different specific binding sites were thought to exist in the fragments. Specific binding of the protein factors to the sites, possibly to the three Mt sequences, may play an important role in the coordinate regulation of the transcription of nuclear genes encoding subunits responsible for mitochondrial oxidative phosphorylation.
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PMID:Common protein-binding sites in the 5'-flanking regions of human genes for cytochrome c1 and ubiquinone-binding protein. 215 70

This paper reports studies of bioenergetic modifications in a TTR1 single-nuclear mutant, isolated as resistant to triethyltin, an inhibitor of mitochondrial ATPase, and effective in cAMP-dependent protein phosphorylation. This mutant appears to have lost the wild-type cell ability to respond to a decrease of oxygen concentration in the growth medium by a decrease of cytochrome concentration in the cell. ATP synthesis rate in mutant cells in both the prestationary and stationary phase of growth appeared increased in comparison to wild-type cells, as too was respiration rate. A comparative study of mitochondria extracted from wild-type and from TTR1 mutant cells showed an increase in respiration rate, an increase in ATP synthesis rate, and an increase in TPP+ uptake in mutant mitochondria. The specific ATPase activity, as well as its sensitivity to TET, appears to be similar for mitochondria extracted from both strains. It was proposed that the modification of mitochondrial biogenesis in the TTR1 mutant may be due to a response of the cell to an increase in ATP hydrolysis caused by the mutation. It is also possible that the modification in cAMP-dependent protein kinase regulation which appeared to occur in this mutant affects protein(s) involved in mitochondrial biogenesis.
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PMID:Mitochondrial modifications in a single nuclear mutant of Saccharomyces cerevisiae affected in cAMP-dependent protein phosphorylation. 216 72

Unilateral ischemia in the right cerebral hemisphere of the rat was induced by ligation of the right common carotid artery coupled with controlled hemorrhage to produce hypotension (25 +/- 8 mm/Hg). Where indicated after 30 min of ischemia, the withdrawn blood was reinfused to restore arterial pressure to normal. Mitochondria isolated from the ipsilateral hemisphere after 30 min of ischemia showed significantly lower respiratory rates than the organelles isolated from the contralateral side. Oxidation of NAD(+)-linked substrates was more sensitive to inhibition in ischemia (30%) than was of ferrocytochrome c (12%), succinate oxidation being intermediate. The activities of membrane-bound dehydrogenases (both NADH and succinate-linked) were also significantly lowered. Ischemia did not affect the cytochrome content of mitochondria. Respiratory activity (NAD(+)-linked) of mitochondria isolated from the ipsilateral hemisphere was twice as sensitive to inhibition by fatty acid as was of preparations from the contralateral side. Mitochondria isolated from cerebral cortex after 90 min of post-ischemic reperfusion showed no significant improvement in the rate of substrate oxidation. Adenine nucleotide translocase activity and energy-dependent Ca2+ uptake, both of which decreased significantly in mitochondria isolated from the ischemic brain, showed little recovery, on reperfusion. These observations suggested the strong possibility that the deleterious effects of ischemia on mitochondrial respiratory function might be mediated by free fatty acids that are known to accumulate in large amounts in ischemic tissues. The pattern of inhibition of ATPase activity was consistent with this view.
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PMID:Influence of cerebral ischemia and post-ischemic reperfusion on mitochondrial oxidative phosphorylation. 234 84

The effects of temperature acclimation of carp upon the hydrocarbon order of intestinal membranes has been determined. A fractionation technique has been developed for the simultaneous purification of brush-border and basolateral membrane fractions from the intestinal mucosa. The specific activity of alkaline phosphatase in the brush-border fraction was enhanced 6.4-fold over that of the initial homogenate, whilst the (Na(+)-K+)-stimulated ATPase was enhanced 5.8-fold in the basolateral fraction. The specific activities of NADPH-cytochrome-c reductase, succinate-cytochrome-c reductase and acid phosphatase were not increased in these two fractions. Membrane hydrocarbon order in membranes from 10 and 30 degrees C-acclimated carp has been compared by measuring the steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene over a range of temperatures. In the brush-border fraction, polarization was identical in both cold- and warm-acclimated groups, whilst large differences were observed in the basolateral fraction sufficient to offset approx. 75% of the temperature-induced ordering effects of cold. The fatty acid composition of the major phosphoglyceride fractions in the brush-border fraction was also largely unaffected by thermal acclimation, whilst the basolateral fraction showed significant increases in the proportion of unsaturated fatty acids in the cold. It is concluded that whilst the basolateral membrane of intestinal mucosa displays a large homoeoviscous response that correlates with a shift in lipid composition, the brush-border membrane does not. These findings are consistent with evidence of functional adaptations of the basolateral membrane during thermal acclimation (Gibson, J.S., Ellory, J.C. and Cossins, A.R. (1985) J. Exp. Biol. 114, 355-364).
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PMID:Temperature adaptation of biological membranes: differential homoeoviscous responses in brush-border and basolateral membranes of carp intestinal mucosa. 237 86

Palmitic acid and gramicidin D at low concentrations uncouple photophosphorylation in a mechanism that is inconsistent with classical uncoupling in the following properties: (1) delta pH, H+ uptake, or the transmembrane electric potential is not inhibited. (2) O2 evolution is stimulated under nonphosphorylating conditions but slightly inhibited in the presence of adenosine 5'-diphosphate + inorganic phosphate (Pi). (3) Light-triggered adenosine 5'-triphosphate (ATP)-Pi exchange is hardly affected, and ATPase activity is only slightly stimulated. (4) ATP-induced delta pH formation is selectively inhibited. This characteristic uncoupling is observed only when the native coupling sites of the electron transport system are used for energization such as for methylviologen-coupled phosphorylation. With pyocyanine, which creates an artificial coupling site, 1000-fold higher gramicidin D and higher palmitic acid concentrations are required for inhibition, and the inhibition is accompanied by a decrease in delta pH. Moreover, comparison between photosystem 1 and photosystem 2 electron transport and the effects of membrane unstacking suggest that low gramicidin D preferentially inhibits photosystem 2, while palmitic acid inhibits more effectively photosystem 1 coupling sites. The inhibitory capacity of fatty acids significantly drops when the chain length is reduced below 16 hydrocarbons or upon introduction of a single double bond in the hydrocarbon chain. It is suggested that palmitic acid and gramicidin D interfere with a direct H+ transfer between specific electron transport and the ATP synthase complexes, which provides an alternative coupling mechanism in parallel with bulk to bulk delta microH+. The sites of inhibition seem to be located in chloroplast ATP synthase, photosystem 2, and the cytochrome b6f complexes.
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PMID:Anomalous uncoupling of photophosphorylation by palmitic acid and by gramicidin D. 245 May 61

White mice, 18-20 g, were fed purified diets containing two weight percent safflower oil plus ten weight percent menhaden, corn, or olive oil for 2 wk. Menhaden oil ingestion resulted in significantly higher levels of 22:6(n-3) and 20:5(n-3), particularly 22:6(n-3), and lower levels of 20:4(n-6) and 18:2(n-6) in cardiac sarcoplasmic reticulum (SR) phospholipids than did corn or olive oil ingestion. These changes in fatty acid composition resulted in a significant decrease in the value of the n-6/n-3 fatty acid ratio of cardiac SR phospholipids. The ratio was 2.8 versus 0.2 in choline phospholipids and 1.9 versus 0.2 in ethanolamine phospholipids in SR of mice fed corn or menhaden oil, respectively. This reduction in the n-6/n-3 fatty acid ratio was associated with a lower relative activity of Ca2+-Mg2+ ATPase, and a lower initial rate of calcium transport and maximum calcium uptake in SR vesicles from mice fed menhaden oil rather than olive or corn oils. The specific activity of NADPH cytochrome C reductase (EC 1.6.2.3) of cardiac SR was not affected by dietary lipids. These data indicate that modification of SR by 22:6(n-3) may change the SR bilayer structure resulting in alteration of the calcium transport properties of SR vesicles. In addition, our results suggest that reduction of calcium flux across cardiac SR following fish oil consumption may also reduce the susceptibility of myocytes to rapid changes in calcium concentrations which may occur during ischemia and reperfusion.
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PMID:Ca2+-Mg2+ ATPase of mouse cardiac sarcoplasmic reticulum is affected by membrane n-6 and n-3 polyunsaturated fatty acid content. 252 49

The effect of rhein on the oxygen consumption, oxidative phosphorylation, ATPase activity and redox state of electron carriers of rat liver mitochondria has been studied. Rhein inhibits ADP- and uncoupler-stimulated respiration on various NAD-linked substrates and succinate, but stimulates state 4 respiration of mitochondria respiring on succinate. Experiments on specific segments of the respiratory chain showed that rhein does not inhibit electron flow through cytochrome oxidase. Electron flow through site 2, the ubiquinone-cytochrome b-cytochrome c1 complex, was also unaffected by rhein, which failed to inhibit the oxidation of duroquinol. Rhein affects oxidative phosphorylation by inhibiting both electron transfer and ADP-driven H+ uptake. The inhibition of succinate oxidation by rhein was found to take place at a point between succinate and ubiquinone, perhaps at the level of succinic dehydrogenase. Spectroscopic evidence demonstrated that rhein induces a NAD(P)H oxidation in mitochondria respiring either on endogenous substrates or on glutamate + malate, and an inhibition of the cytochrome b reduction by succinate. These observations, together with other evidence, suggest that rhein inhibits electron transport in rat liver mitochondria at the dehydrogenase-coenzyme level, particularly when the electron carriers are in a relatively oxidized state and/or when the inner membrane-matrix compartment is in the condensed state.
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PMID:Sites of inhibition of mitochondrial electron transport by rhein. 252 79

The amphiphilic cationic cardioactive drugs (pindolol, propranolol and amiodarone) were tested for their effects on lipid dynamics (measured by fluorescence depolarization) and on enzymatic activities up to 1 mM in purified cardiac sarcolemmal vesicles from adult rat. The vesicles were enriched 12- to 37-fold (with respect to tissue homogenate) in Na+/K+ ATPase, K+-stimulated p-nitrophenylphosphatase, 5'nucleotidase and adenylate cyclase, all of which are believed to be components of sarcolemma. Phospholipids and cholesterol content were enriched 5- and 13-fold respectively. There was very little contamination of the sarcolemmal vesicles by sarcoplasmic reticulum (as judged by Ca2+ ATPase and glucose-6-phosphatase activities) or mitochondria (as judged by cytochrome-c-oxidase activity). Pindolol had no effect on lipid dynamics and enzyme activities except for the isoproterenol-stimulated adenylate cyclase. The latter was also totally inhibited at 1 microM by propranolol which inhibited Mg2+ ATPase and increased fluidity above 20 microM. Amiodarone affected all the enzyme activities (except Na+/K+ ATPase): isoproterenol-stimulated adenylate (IC50 = 30 microM), Mg2+ ATPase (IC50 = 20 microM) and K+-stimulated-p-nitrophenylphosphatase were inhibited; 5'nucleotidase was activated above 2 microM. By contrast with propranolol, amiodarone decreased lipid mobility. The effect was linear with the concentration of the drug above 1 microM.
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PMID:Differential effects of amiodarone and propranolol on lipid dynamics and enzymatic activities in cardiac sarcolemmal membranes. 253 21

We have identified a 19 kd protein of the mitochondrial outer membrane (MOM19). Monospecific IgG and Fab fragments directed against MOM19 inhibit import of precursor proteins destined for the various mitochondrial subcompartments, including porin, cytochrome c1, Fe/S protein, F0 ATPase subunit 9, and F1 ATPase subunit beta. Inhibition occurs at the level of high affinity binding of precursors to mitochondria. Consistent with previous functional studies that suggested the existence of distinct import sites for ADP/ATP carrier and cytochrome c, we find that import of those precursors is not inhibited. We conclude that MOM19 is identical to, or closely associated with, a specific mitochondrial import receptor.
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PMID:MOM19, an import receptor for mitochondrial precursor proteins. 255 58


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