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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)

Nucleotide-depleted F1-ATPase from Escherichia coli was reconstituted with F1-depleted membranes and shown to catalyze high rates of oxidative phosphorylation of ADP and GDP. Adenine nucleotide became bound to the nonexchangeable nucleotide sites on membrane-bound F1 during ATP synthesis, but binding of guanine nucleotides to nonexchangeable sites during GTP synthesis was not detectable. It was possible to reload the nonexchangeable sites on nucleotide-depleted F1 with radioactive adenine nucleotide prior to membrane reconstitution. The radioactive adenine nucleotide did not exchange significantly during oxidative phosphorylation of ADP or GDP. The amount of nonexchangeable adenine nucleotide found in membrane-bound F1 was the same when the nonexchangeable sites were reloaded either prior to membrane reconstitution of the F1 or after membrane reconstitution with nucleotide-free F1 followed by a burst of oxidative phosphorylation of ADP. The results showed that occupation of the nonexchangeable sites on F1 by tightly bound nucleotide is not required for oxidative phosphorylation of GDP (a physiological activity of F1 in the bacterial cell). Also, the results confirm directly that the adenine-specific nonexchangeable sites on F1 are noncatalytic sites. Using this experimental approach, it was possible to look for a regulatory effect of the nonexchangeable nucleotide on oxidative phosphorylation. Nucleotide-depleted F1 was first reloaded with (i) ATP, (ii) ADP, (iii) 5'-adenylyl imidodiphosphate, or (iv) zero nucleotide, and was then reconstituted with F1-depleted membranes. The reconstituted membranes were compared in respect to rates of oxidative phosphorylation of GDP and Km values of GDP and Pi. No regulatory role for the nonexchangeable nucleotide was evident.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Catalytic properties of the Escherichia coli proton adenosinetriphosphatase: evidence that nucleotide bound at noncatalytic sites is not involved in regulation of oxidative phosphorylation. 286 99

Adenine nucleotide translocase (AdNT) levels were measured as the exchange of extramitochondrial against intramitochondrial adenosine diphosphate (ADP) in liver, spleen, and testes mitochondria isolated from normal and hypothyroid rats using the "back-exchange" and atractyloside-stop method of Pfaff and Klingenberg. The results provide confirmation of previous reports that mitochondria from hypothyroid rats show a markedly diminished AdNT activity, which is restored to normal levels within 72 hours by intraperitoneal injection of 10 to 20 micrograms triiodothyronine (T3)/100 g body weight. The latter dose was found in dose-response studies to result in maximal stimulation of AdNT in liver mitochondria. Qualitatively similar results on AdNT activity were obtained in liver mitochondria within 30 to 60 minutes following intravenous injection into hypothyroid rats of a more physiological dose of T3 (40 ng/100 g body weight). AdNT in mitochondria isolated from spleen and testes (organs that do not exhibit a calorigenic response after administration of thyroid hormone to the whole animal) failed to respond to thyroidectomy and to administration of T3. More recently, we have observed that in vitro replacement of T3 also stimulates AdNT activity in hypothyroid liver mitochondria. The enzyme adenosine triphosphate (ATP) synthase was examined as another possible candidate for direct hormonal stimulation of mitochondria. Simultaneous determinations on the same rats after intraperitoneal injection of T3 (20 micrograms/100 g body weight) showed little or no effect on ATP synthase until after 37 to 85 hours, whereas enhanced activity of the translocator was regularly observed at 17 hours.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Thyroid hormone action: effect of triiodothyronine on mitochondrial adenine nucleotide translocase in vivo and in vitro. 786 15

Consideration is made here of the ability of He-Ne laser light to affect both transport and enzymic reactions by acting on substrates. Adenine nucleotides irradiated with 3 Joules/cm2 fluence (10 mW/cm2 fluence rate) showed altered biochemical behaviour when used as substrates for certain mitochondrial reactions in isolated rat liver mitochondria: ADP/ATP antiport and ATP synthase, which allow for oxidative phosphorylation, and adenylate kinase reaction. In order to determine ATP synthase kinetics a specific method was developed which allows for calculation of ADP phosphorylation rate in intact mitochondria. While no change in ATP synthase kinetics was observed as a result of ADP irradiation, adenine nucleotides proved to be sensitive to He-Ne laser irradiation when their interaction with ADP/ATP carrier and adenylate kinase was considered.
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PMID:A novel property of adenine nucleotides: sensitivity to helium-neon laser in mitochondrial reactions. 909 Apr 52

The catalytic portion of the chloroplast ATP synthase (CF(1)) consists of five different polypeptides in the stoichiometry alpha(3)beta(3)gammadeltaepsilon and is structurally asymmetric. Asymmetry is readily apparent in the properties of the six nucleotide binding sites and the single-copy, smaller subunits. Asymmetry is also detected in the alpha subunits by the rapid and covalent binding of Lucifer Yellow vinyl sulfone (LY) to one of the three chemically identical alpha subunits. The binding of LY to a single alpha subunit has allowed the investigation of whether asymmetry in the alpha subunits is a permanent feature of CF(1). The development of an electrochemical proton gradient across illuminated thylakoid membranes and the preincubation of CF(1) in solution with Mg(2+)-ATP were found to alter the LY distribution such that multiple alpha subunits were labeled with LY. Illumination of thylakoid membranes doubled the extent of LY labeling, and fluorescence resonance energy transfer measurements indicated that LY was bound to more than one alpha subunit. Since the change in LY distribution was inhibited by proton ionophores (uncouplers), alteration of alpha conformation by illumination is a result of the generation of a proton gradient. Preincubation of CF(1) in solution with Mg(2+)-ATP had no effect on the extent of LY labeling but resulted in multiple alpha subunits binding LY as determined by fluorescence resonance energy transfer measurements. Adenine nucleotides at substrate level concentrations inhibit the reaction of LY with the alpha subunits. No increase in LY labeling was observed when thylakoids were illuminated under conditions in which CF(1) was catalytically active.
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PMID:Influences of energization and nucleotide binding on the reaction of Lucifer Yellow vinyl sulfone with the alpha subunits of the chloroplast ATP synthase. 1075 88

The mitochondrial oxidative phosphorylation involves five multimeric complexes imbedded in the inner membrane: complex I (Nicotinamide Adenine Dinucleotide (NADH) quinone oxidoreductase), II (succinate dehydrogenase), III (ubiquinol cytochrome c oxido reductase or bc1 complex), IV (cytochrome c oxidase), and V (ATP synthase). These respiratory complexes are conserved from the yeast Saccharomyces cerevisiae to human with the exception of complex I, which is replaced by three NADH dehydrogenases in S. cerevisiae. Here, we provide several protocols allowing an exhaustive characterization of each yeast complex: this chapter describes procedures from mitochondria preparation to measurement of the activity of each complex and analysis of their subunit composition and provides information on the interactions between different complexes.
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PMID:Preparation of respiratory chain complexes from Saccharomyces cerevisiae wild-type and mutant mitochondria : activity measurement and subunit composition analysis. 1837 11

Mitochondria represent cell "powerhouses," being involved in energy transduction from the electrochemical gradient to ATP synthesis. The morphology of their cell types may change, according to various metabolic processes or osmotic pressure. A new morphology of the inner membrane and mitochondrial cristae, significantly different from the previous one, has been proposed for the inner membrane and mitochondrial cristae, based on the technique of electron tomography. Mitochondrial Ca(2+) transport (the transporter has been isolated) generates reactive oxygen species and induces the mitochondrial permeability transition of both inner and outer mitochondrial membranes, leading to induction of necrosis and apoptosis. In the mitochondria of several cell types (liver, kidney, and heart), mitochondrial oxidative stress is an essential step in the induction of cell death, although not in brain, in which the phenomenon is caused by a different mechanism. Mitochondrial permeability transition drives both apoptosis and necrosis, whereas mitochondrial outer membrane permeability is characteristic of apoptosis. Adenine nucleotide translocase remains the most important component involved in membrane permeability, with the opening of the transition pore, although other proteins, such as ATP synthase or phosphate carriers, have been proposed. Intrinsic cell death is triggered by the release from mitochondria of proteic factors, such as cytochrome c, apoptosis inducing factor, and Smac/DIABLO, with the activation of caspases upon mitochondrial permeability transition or mitochondrial outer membrane permeability induction. Mitochondrial permeability transition induces the permeability of the inner membrane in sites in contact with the outer membrane; mitochondrial outer membrane permeability forms channels on the outer membrane by means of various stimuli involving Bcl-2 family proteins. The biologically active amines, spermine, and agmatine, have specific functions on mitochondria which distinguish them from other amines. Enzymatic oxidative deamination of spermine by amine oxidases in tumor cells may produce reactive oxygen species, leading to transition pore opening and apoptosis. This process could be exploited as a new therapeutic strategy to combat cancer.
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PMID:Milestones and recent discoveries on cell death mediated by mitochondria and their interactions with biologically active amines. 2761 11