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)

Bovine heart submitochondrial particles incubated with a low concentration of ADP in the presence of Mg2+ and passed through a Sephadex column equilibrated with EDTA exhibit sensitivity of their initial ATPase activity to preincubation with Mg2+. By using particles thus prepared, several characteristics of a Mg(2+)-specific inhibitory site on F0.F1 ATPase were studied. The inhibition was shown to be both time- and Mg(2+)-concentration-dependent, with an equilibrium constant (at infinite time) of 2 x 10(-6) M (25 degrees C, pH 7.5). The dependence of the pseudo-first-order rate constant for the inhibition process on Mg2+ concentration suggests the presence of a single Mg(2+)-binding site with K8 = 1.1 x 10(-4) M. The data obtained are consistent with a two-step mechanism of Mg(2+)-F0.F1 interaction which results in a loss of the ATPase activity; it includes rapid pH-dependent binding of Mg2+ at the site with K8 = 1.1 x 10(-4) M, followed by a slow interconversion of the Mg(2+)-F1 complex into inactive ATPase (kin. = 0.65 min-1, kact. = 0.01 min-1). The Mg(2+)-inhibited ATPase is very slowly (t1/2 approximately 90 min) re-activated in the presence of EDTA. The rate of EDTA-induced re-activation is pH-independent and can be dramatically increased by added ATP, Pi and sulphite. The dissociation constants for free ATP and P1 (5 x 10(-7) M and 1 x 10(-3) M respectively) and the maximal activation rates were determined by measuring the hyperbolic dependencies of the EDTA-induced re-activation of Mg(2+)-de-activated ATPase on the concentrations of the accelerating ligands. Taken together, the data obtained show two functionally detectable free nucleotide-specific binding sites, one site for Pi and one Mg(2+)-specific ATPase-inhibitory site on the F0.F1 mitochondrial ATP synthase complex.
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PMID:Interaction of Mg2+ with F0.F1 mitochondrial ATPase as related to its slow active/inactive transition. 182 47

The alpha 3 beta 3 complex of ATP synthase obtained from a thermophilic bacterium PS3 was isolated and found to show the ATPase activity (Kagawa, Y., Ohta, S., and Otawara-Hamamoto, Y. (1989) FEBS Lett. 249, 67-69). The structure and the nucleotide binding effects of the alpha 3 beta 3 complex were investigated by means of small-angle x-ray scattering and high performance liquid chromatography. The scattering profile from the alpha 3 beta 3 complex was explained with a model in which the complex is made of an ellipsoid of revolution with the axes of 121.8, 121.8, and 72.0 A having an elliptical hollow cavity with the axes of 35.4, 35.4, and 72.0 A. By the addition of Mg.AT(D)P, significant changes in the scattering profile were observed, in which the radius of gyration decreased from 44 to 35 A. This change was found by gel filtration to be caused by the dissociation reaction from the alpha 3 beta 3 hexamer to the alpha beta dimer. The dissociation of the alpha 3 beta 3 complex was not induced by unhydrolyzable ATP analogue, nor by Pi, Mg2+, and Pi + Mg2+. The structure of the dimer was well explained by the triaxial ellipsoidal model with the axes of 105.2, 39.4, and 108.2 A. The dissociation into the dimer is considered to be related to the ATPase activity because the AT(D)P-induced dissociation is observed only in the presence of Mg2+ ions.
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PMID:Small-angle X-ray scattering studies of Mg.AT(D)P-induced hexamer to dimer dissociation in the reconstituted alpha 3 beta 3 complex of ATP synthase from thermophilic bacterium PS3. 182

Activities of the mitochondrial ATP synthase and the electron transfer chain were investigated in cultured cardiomyocytes prepared from untreated and thyroxine-treated rats. Quiescent cells from the thyroxine-treated animals showed a 33% increase in mitochondrial ATP synthase capacity, but no change in respiratory chain capacity, relative to those from control animals. This increase was attributable largely to (a) a 25% increase in F1 content in these mitochondria, and partly to (b) a 10% stimulation in ATPase activity due to raised intramitochondrial Ca2+. Both types of cell showed a normal ATP content of 38-40 nmol/mg cell protein. In control cells, the mitochondrial ATP synthase responded to increased energy demand (by electrical stimulation and/or by positive inotropic agents) with an increase in its capacity of up to 2-fold. This response was absent in cells from thyroxine-treated animals. In addition, cellular ATP levels fell significantly after 2 min electrical stimulation of cells from thyroxine-treated animals, while those of control cells were constant. It was concluded that regulation of the mitochondrial ATP synthase was defective in heart cells from thyroxine treated rats, leading to an energy deficit when energy demand on the cells was increased. Animals treated with thyroxine, but allowed to recover for 17 days after treatment, showed responses indistinguishable from the control cells. Thus, the effects of thyroxine on mitochondrial activities were reversible.
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PMID:Control of mitochondrial ATP synthase in rat cardiomyocytes: effects of thyroid hormone. 182 41

A novel, simple, and rapid preparative method for purification of rat liver H(+)-ATP synthase by anion-exchange HPLC was developed. The H(+)-ATP synthase purified had higher ATPase activity in the absence of added phospholipids than any preparation reported previously, and this activity was completely inhibited by oligomycin. When reconstituted into proteoliposomes, the H(+)-ATP synthase showed an ATP-dependent 8-anilinonaphthalene-1-sulfonate response and ATP-Pi exchange activity, both of which were also completely inhibited by oligomycin and an uncoupler, indicating the intactness of the H(+)-ATP synthase. An immunochemical study and a labeling experiment with N,N'-[14C]dicyclohexylcarbodiimide ([14C]DCCD) demonstrated the presence of chargerin II ( a product of mitochondrial A6L DNA) and DCCD-binding protein (subunit c) in the complex. The subunits of the complex were separated into 11 main fractions by reverse-phase HPLC, and 3 of them and the delta subunit in F1 were partially sequenced. A search for sequence homologies indicated that these components were subunit b, coupling factor 6, subunit delta, and subunit epsilon. This is the first report of the existence of subunit b, factor 6, and chargerin II in H(+)-ATP synthase purified from rat liver mitochondria.
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PMID:H(+)-ATP synthase from rat liver mitochondria. A simple, rapid purification method of the functional complex and its characterization. 182 63

The requirement of bovine heart mitochondrial oligomycin sensitivity conferring protein (OSCP) in conferring dicyclohexylcarbodiimide (DCCD)-sensitivity to membrane-bound F1 was investigated by using OSCP-depleted membrane fraction (UF0) of ATP synthase. The ATPase activity of UF0-F1 was completely insensitive to DCCD while that of UF0-F1-OSCP was inhibited 95% by 16 microM DCCD. Both UF0-F1 and UF0-F1-OSCP complexes bound 5 nmol [14C]DCCD/mg UF0, and all the radioactivity was found to be associated with the DCCD-binding proteolipid. The data suggest that OSCP may be necessary for transmitting not only energy-linked signals, but also signals induced by F0 inhibitory ligands in mitochondrial energy transduction.
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PMID:ATP synthase complex from bovine heart mitochondria: the oligomycin sensitivity conferring protein is essential for dicyclohexyl carbodiimide-sensitive ATPase. 183 60

The Schizosaccharomyces pombe nuclear gene, atp2, encoding the beta subunit of the mitochondrial ATP synthase, was sequenced and found to contain a 1575-bp open reading frame. Two adjacent transcription-initiation sites were found at positions 34 and 44 nucleotides upstream of the translation-initiation codon. The deduced polypeptide sequence was composed of 525 amino acid residues (molecular mass = 56875 Da). The mature polypeptide starts at residue 45 (molecular mass = 51,685 Da), indicating the presence of a presequence of 44 residues, presumably involved in mitochondrial targeting. The atp2 mutant B59-1 [Boutry, M. & Goffeau, A. (1982) Eur. J. Biochem. 125, 471-477] and its related revertant allele R4-3 [Jault, J. M., Di Pietro, A., Falson, P., Gautheron, D. C., Boutry, M. & Goffeau, A. (1989) Biochem. Biophys. Res. Commun. 158, 392-399] were also cloned and sequenced. A single nonsense mutation, CAG (Gln170)----TAG (stop) in mutant B59-1, became a missense mutation, TAG (stop)----TAC (Tyr) in revertant R4-3. Gln170 is located between the first and second elements belonging to the nucleotide-binding site. Its substitution by a tyrosine residue increases the enzyme affinity towards ADP, the amount of endogenous nucleotides and the apparent negative cooperativity for ATPase activity.
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PMID:Beta subunit of mitochondrial F1-ATPase from the fission yeast. Deduced sequence of the wild type protein and identification of a mutation that increases nucleotide binding. 183 60

The subunit analogous to the d-subunit of ATP synthase from bovine heart mitochondria was isolated from the purified yeast enzyme. Partial protein sequences were determined by direct methods. From this information, two oligonucleotide probes were constructed and used for screening a DNA genomic bank of Saccharomyces cerevisiae. The sequence of yeast subunit d was deduced from the DNA sequence of ATP7 gene. Mature yeast subunit d is 173 amino acids long. Its NH2-terminal serine is blocked by an N-acetyl group, and the protein has no processed NH2-terminal sequence other than the removal of the initiator methionine. The protein is predominantly hydrophilic. The amino acid sequence is 22% identical and 44% homologous to bovine subunit d. A null mutant was constructed. The mutant strain was unable to grow on glycerol medium. The mutant mitochondria had no detectable oligomycin-sensitive ATPase activity, and the catalytic sector F1 was loosely bound to the membranous part. The mutant mitochondria did not contain subunit d, and the mitochondrially encoded hydrophobic subunit 6 was not present.
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PMID:ATP synthase of yeast mitochondria. Characterization of subunit d and sequence analysis of the structural gene ATP7. 183 57

The head piece of the A-type ATP synthase in an extremely halophilic archaebacterium, namely Halobacterium salinarium (halobium), is composed of two kinds of subunit, alpha and beta, and is associated with ATP-hydrolyzing activity. The genes encoding these subunits with hydrolytic activity have been cloned and sequenced. The putative amino acid sequences of the alpha and beta subunits deduced from the nucleotide sequences of the genomic DNA consist of 585 and 471 residues, respectively. The amino acid sequence of the alpha subunit of the halobacterial ATPase is 63 and 49% identical to the alpha subunits of ATPases from two other archaebacteria, Methanosarcina barkeri and Sulfolobus acidocaldarius, respectively. The sequence of the beta subunit is 66 and 55% identical to the beta subunits from these respective organisms. The homology between the alpha and beta subunits is around 30%. In contrast, the sequences of the halobacterial ATPase is less than 30% identical to F1 ATPase when any combination of subunits is considered. However, they are greater than 50% identical to a eukaryotic vacuolar ATPase when alpha and a, beta and b combinations are considered. These data fully confirm the first demonstration of this kind of relationship which was achieved by immunoblotting with an antibody raised against the halobacterial ATPase. We concluded that the archaebacterial ATP synthase is an A-type and not an F-type ATPase. This classification is also demonstrated by a "rooted" phylogenetic tree where halobacteria locate close to other archaebacteria and eukaryotes and distant from eubacteria.
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PMID:The ATP synthase of Halobacterium salinarium (halobium) is an archaebacterial type as revealed from the amino acid sequences of its two major subunits. 183 29

The mitochondrial H(+)-ATPase of the parasitic protozoan Trypanosoma brucei is shown to be developmentally regulated through the T. brucei life cycle as has been shown for components of the mitochondrial electron transport chain. We have substantiated our results by assaying not only for oligomycin-sensitive ATPase activity but also by determining the level of ATP synthetic activity. These results show that the level of ATPase present in the procyclic form of T. brucei is increased by at least threefold from that of the early bloodstream form while the ATPase activity in the late bloodstream form is only about twofold higher than the early form. ATP synthesis activity shows these same results. We have determined the level of ATP synthase protein present in the life cycle stages by Western analysis employing the antibodies that we have raised against both the water soluble F1 and the membrane-associated F0 moieties which we have purified from T. brucei. The Western blots of the procyclic form show strong reactivity with both the F0 and F1 antibodies. The other two life cycle stages, the early and the late bloodstream forms, show considerably less reactivity, paralleling the activity results. Electron micrographs of the sonicated mitochondrial fraction show inverted vesicles which are studded with knobby H(+)-ATPase in the procyclic form. The early bloodstream vesicles show very few of these characteristic structures, while the late bloodstream form shows a range of vesicles from nearly nude to partially studded.
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PMID:The mitochondrial ATP synthase of Trypanosoma brucei: developmental regulation through the life cycle. 183 42

Inactivation of the isolated ATPase portion of ATP synthase from beef-heart mitochondria (F1) by its natural inhibitor protein (IP) during steady-state ATP hydrolysis is accompanied by a trapping of 1 mol nucleotide/mol F1 in one of the catalytic sites. The trapped nucleotide is not released during incubation of IP-inhibited F1 in the presence of MgATP at pH 8.0 for at least 20 min, indicating a very low turnover rate of the IP.F1 complex. The ATP/ADP ratio of the trapped nucleotides is higher than that found for transitorily bound nucleotides under the same conditions but in the absence of IP. The IP impairs the acceleration of ATP hydrolysis and product release steps that results from the binding of ATP to an alternate catalytic site. It also inhibits ATP hydrolysis by a single catalytic site or shifts the equilibrium toward ATP formation from bound ADP and Pi. At high pH, an active acidic form of the free IP is transformed to the inactive basic one with a half-time of 3-4 s. This process seems to be prevented by IP binding to F1. The inactive basic form of IP does not compete with the active acidic IP for the binding to F1. The data do not favor the existence of a long-lived catalytically active IP.F1 intermediate during IP action on F1. The reactivation of IP-inhibited membrane-bound F1 by energization may be due to a conformational change in the IP.F1 complex allowing the transformation of IP into an inactive basic state that rapidly dissociates.
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PMID:When beef-heart mitochondrial F1-ATPase is inhibited by inhibitor protein a nucleotide is trapped in one of the catalytic sites. 183 93


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