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:3.6.3.14 (ATP synthase)
7,042 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of temperature on the activation energies of mitochondrial enzymes of the yeast Saccharomyces cerevisiae was examined. Non-linear Arrhenius plots with discontinuities in the temperature range 14-19 degrees C and 19-22 degrees C were observed for the respiratory enzymes and mitochondrial ATPase (adenosine triphosphatase) respectively. A straight-line Arrhenius plot was observed for the matrix enzyme, malate dehydrogenase. The activation energies of the enzymes associated with succinate oxidation, namely, succinate oxidase, succinate dehydrogenase and succinate-cytochrome c oxidoreductase, were in the range 60-85kJ/mol above the transition temperature and 90-160kJ/mol below the transition temperature. In contrast, the corresponding enzymes associated with NADH oxidation showed significantly lower activation energies, 20-35kJ/mol above and 40-85kJ/mol below the transition temperature. The discontinuities in the Arrhenius plots were still observed after sonication, treatment with non-ionic detergents or freezing and thawing of the mitochondrial membranes. Discontinuities for cytochrome c oxidase activity were only observed in freshly isolated mitochondria, and no distinct breaks were observed after storage at -20 degrees C. Mitochondrial ATPase activity still showed discontinuities after sonication and freezing and thawing, but a linear plot was observed after treatment with non-ionic detergents. The results indicate that the various enzymes of the respiratory chain are located in a similar lipid macroenvironment within the mitochondrial membrane.
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PMID:Phase transitions in yeast mitochondrial membranes. The effect of temperature on the energies of activation of the respiratory enzymes of Saccharomyces cerevisiae. 16 75

The levels of several enzymes have been studied during sporulation of Saccharomyces cerevisia. The specific activities of ribonuclease and aminopeptidase I raised several-fold after transfer of the cells to sporulation medium, whereas the specific activities of phosphofructokinase, glucose-6-phosphate dehydrogenase, tryptophan synthase and pyruvate decarboxylase were not significantly altered. The specific activities of NAD-dependent glutamate dehydrogenase, isocitrate lyase, malate dehydrogenase and fructose bisphosphatase all decreased from the onset of sporulation. The inactivation of these latter enzymes was inhibited by cycloheximide and by inhibitors of energy metabolism. Hexokinase, alcohol dehydrogenase and glutamate oxaloacetate transaminase were partially lost from the cells during the period of ascus maturation. None of the enzyme changes observed proved to be 'sporulation-specific' in that it occurred exclusively in sporulating diploid yeast cells. Therefore it is postulated that the meiotic events and the metabolic changes required for ascospore formation are under separate genetic control in this organism. During sporulation, the cellular content of cytochromes b, c, and aa3 was reduced to 20% or less of that present in vegetative derepressed cells. Since the relative percentage of total to cycloheximide-insensitive mitochondrial protein synthesis was not significantly altered throughout sporulation, and the pattern of mitochondrially synthesized polypeptides was rather similar both in vegetative and in sporulating cells, it appeared that not only degradation but also synthesis and therefore turnover of the mitochondrially coded polypeptides of cytochromes b and aa3 took place during sporulation. The activity ratio of cytochrome c oxidase to F1-ATPase in submitochondrial particles isolated from vegetative cells and from purified asci was almost identical. This indicates that the loss of membrane-bound mitochondrial cytochromes during sporulation is probably due to a nonselective degradation of inner mitochondrial membrane proteins.
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PMID:Protein degradation during yeast sporulation. Enzyme and cytochrome patterns. 18 44

Oxidation of ferrocytochrome c by molecular oxygen catalysed by cytochrome c oxidase (cytochrome aa3) is coupled to translocation of H+ ions across the mitochondrial membrane. The proton pump is an intrinsic property of the cytochrome c oxidase complex as revealed by studies with phospholipid vesicles inlayed with the purified enzyme. As the conformation of cytochrome aa3 is specifically sensitive to the electrochemical proton gradient across the mitochondrial membrane, it is likely that redox energy is primarily conserved as a conformational "strain" in the cytochrome aa3 complex, followed by relaxation linked to proton translocation. Similar principles of energy conservation and transduction may apply on other respiratory chain complexes and on mitochondrial ATP synthase.
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PMID:The mechanism of energy conservation and transduction by mitochondrial cytochrome c oxidase. 20 Dec 86

This paper reviews mechanisms by which the rate of synthesis of subunits of mitochondrial inner membrane protein complexes and the assembly of these subunits are co-ordinated. Current models are evaluated and critically discussed in the light of some recent evidences. The focus is on the incorporation of cytoplasmically-synthesized cytochrome c oxidase subunits in the development of a newer model, which introduces some twists into a combination of several current ideas. A mechanism which governs both organized assembly and the co-ordination of rates of polypeptide synthesis is illustrated and the principles of the model are applied to the elucidation of some odd features of certain mutants. The possibilities that mitochondrial ATPase and cytochrome c reductase may also be synthesized and assembled according to this model are discussed.
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PMID:Biosynthesis of mitochondrial membrane proteins: co-ordination with special reference to cytochrome c oxidase. 20 73

Steady-state levels of the mitochondrial rRNAs, of mRNAs for mitochondrially and nuclear-encoded subunits of cytochrome c oxidase and for the beta subunit of ATP synthase were assessed by Northern blot hybridizations during the in vitro differentiation of human myoblasts. Transcript levels of the so-called liver-type form of subunit VIa of cytochrome c oxidase diminished during the course of differentiation, while transcription of the so-called heart-type form was induced. Transcripts for the liver-type form and for the heart-type form of subunit VIIa of cytochrome c oxidase were detected in all myogenic cultures; the levels of the heart-type form progressively increased during the course of differentiation. The levels of the other transcripts studied did not change substantially. The results suggest subunit switching of subunit VIa and co-expression of subunit VIIa isoforms during myogenesis. The differential changes in mRNA levels of the heart-type subunits VIa and VIIa and the differential changes in mRNA levels of the liver-type subunits VIa and VIIa demonstrate that different transcriptional regulation mechanisms are present for both heart-type genes as well as for both liver-type genes.
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PMID:Steady-state transcript levels of cytochrome c oxidase genes during human myogenesis indicate subunit switching of subunit VIa and co-expression of subunit VIIa isoforms. 131 12

The presence of an ATPase on yeast peroxisomal membranes was studied by immunological methods. Western blot analysis of purified peroxisomal membranes from several yeasts revealed distinct cross-reaction with specific antibodies against the F1-part or the beta-subunit of the mitochondrial ATPase of Saccharomyces cerevisiae. This was not due to mitochondrial contamination as was demonstrated by analytical sucrose gradient centrifugation. Protein A-gold labelling carried out on Lowicryl-embedded methanol-grown Hansenula polymorpha using these antibodies did not result in significant staining. However, when organelles isolated from this yeast were successively incubated with antibodies and protein A-gold prior to embedding, specific labelling was observed on both the peroxisomal membrane and the membrane of damaged mitochondria but not on intact mitochondria. Specific labelling of the peroxisomal membrane was confirmed by freeze-fracture immunocytochemistry. In addition to the peroxisomal membrane, the mitochondrial membrane was also labelled in these experiments. Freeze-fracture immunocytochemistry was also successful for the localization of peroxisomal matrix proteins, e.g. alcohol oxidase and dihydroxyacetone synthase, and of mitochondrial membrane proteins, e.g. cytochrome c oxidase.
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PMID:Immunocytochemical demonstration of the peroxisomal ATPase of yeasts. 213 97

In a patient with mitochondrial myopathy, the defect of cytochrome c oxidase activity was restricted to some muscle fibers. To isolate cell lines with or without oxidase activity from a single muscle sample, primary cultured cells were transformed by replication origin-defective simian virus 40, and then cloned. The clones were examined by cytochemical staining for cytochrome c oxidase activity. Eight myogenic clones were completely devoid of activity, while the other myogenic and nonmyogenic clones were not. Deficiency of cytochrome c oxidase was stable in culture for at least a year after serial passaging. The amount of mitochondrial DNA in cytochrome c oxidase-deficient cells was the same as in control cells, and no deletion in the mitochondrial DNA was detected. Protein synthesis in mitochondria of the subunits of cytochrome c oxidase and subunit 6 of the ATP synthase complex was markedly decreased, whereas synthesis of the other subunits encoded by mitochondrial DNA was normal. These cloned cell lines provide an excellent system for clarifying the cause of mitochondrial myopathy and for investigating nuclear-mitochondrial genetic interaction.
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PMID:Cytochrome c oxidase--deficient myogenic cell lines in mitochondrial myopathy. 254 62

One polypeptide subunit of cytochrome c oxidase (EC 1.9.3.1) and two subunits of the ATPase/ATP synthase (EC 3.6.1.34) in mitochondria of Neurospora crassa are covalently modified with a derivative of pantothenic acid. In asexual spores of a pantothenate auxotroph of Neurospora, deprivation of pantothenic acid blocked the increase of the specific activities of cytochrome c oxidase and the ATPase above the basal activities in the dormant spores. Under cellular panthothenate deprivation, all the subunit peptides of these two enzymes apparently were synthesized and accumulated in the mitochondria, but these subunits were not assembled into normal complexes, and 55Fe-labeled heme a was incorporated into immunoprecipitable cytochrome c oxidase to a very low extent. In pantothenate-supplemented cells, the pantothenate derivative apparently is attached to the free unassembled subunits and appears not to be present in the assembled enzymes. It is likely that cellular deprivation of pantothenate, resulting in failure to modify the three subunit peptides, causes an interruption of the assembly pathway of cytochrome c oxidase and the ATPase/ATP synthase.
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PMID:Pantothenate is required in Neurospora crassa for assembly of subunit peptides of cytochrome c oxidase and ATPase/ATP synthase. 287 72

It has been proposed that the acquisition of efficient energy-transducing mitochondria after birth is mediated by an ATP-dependent mechanism "that causes the rapid maturation of mitochondria without requiring either transcription or translation" (Pollak, J. K., and Sutton, R. (1980) Trends Biochem. Sci. 5, 23-27). Investigation of developmental changes in rat liver mitochondria during the first 6 postnatal h showed that fetal mitochondria had low State 4, State 3, and uncoupled rates of respiration, inefficient coupling between respiration and phosphorylation, and low membrane potentials and proton electrochemical gradients under State 4 conditions. In contrast, hepatic mitochondria from 1-h-old neonates showed increased respiratory control and ADP/O ratios and adult proton electrochemical gradient and membrane potential values. In parallel with these changes, mitochondria became enriched in adenine nucleotides and underwent a 50% reduction in matrix volume. During the first postnatal hour, an increase in mitochondrial succinic dehydrogenase, cytochrome c oxidase, and F1-ATPase activities takes place in the neonatal liver concurrent with a preferential postnatal increase in the in vivo rates of protein synthesis for mitochondrial proteins. In particular, the amount of F1-ATPase increased from 109 +/- 9 to 206 +/- 5 ng/microgram of mitochondrial protein in the first hour of postnatal life. Inhibitors of cytosolic protein synthesis present during the first 2 h of life blocked the postnatal increase in respiratory control and ADP/O ratios, succinic dehydrogenase activity, and F1-ATPase content; but they had no effect on the increase in adenine nucleotide concentrations and mitochondrial volume contraction. This indicates that the acquisition of an efficient coupling between respiration and phosphorylation is dependent on de novo protein synthesis and cannot be brought about by the postnatal increase in adenine nucleotides. The increase of State 4 and uncoupled rates of respiration during the first 2 postnatal h was resistant to protein synthesis inhibitors. We suggest that the postnatal increase in these parameters is due to the reduction of mitochondrial volume occurring during that time, which, in turn, may be triggered by the concurrent enrichment in adenine nucleotides.
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PMID:Postnatal development of rat liver mitochondrial functions. The roles of protein synthesis and of adenine nucleotides. 289 64

Bovine cardiac muscle was extracted by an acidic chloroform/methanol mixture. A combination of gel permeation and ion-exchange chromatographies in organic solvents and HPLC allowed the purification of subunits VIIIa (Mr 5400) and VIIIb (Mr 4900) of cytochrome c oxidase and of A6L protein (Mr 7900) of ATP synthase. The identification of the proteins was made possible by measurement of their molecular weight by fast atom bombardment-mass spectrometry (FAB-MS) in conjunction with conventional Edman degradation. The determination by FAB-MS of the molecular weight of A6L protein confirmed its supposed formylated N-terminal methionine.
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PMID:Purification and characterization of low-molecular-weight beef heart proteolipids: use of fast atom bombardment-mass spectrometry for identification. 290 96


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