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)

Isolated myocytes from ventricles are quiescent in the presence of 0.9 mM calcium. However, it is possible to induce beating by adding 0.5 mM BaCl2 to the media or to induce a contracture by elevating the external concentration of potassium (72.5 mM K). During the viable stage of contracture, which is up to 1 h, the sarcomere spacing is 1.7 +/- 0.1 micron and no leakage of intracellular components is observed. The metabolic properties of the cells in quiescent, beating and contracted states were compared. The O2 consumption (natom per mg cell protein per min) increased from 10-11 in quiescent cells to 60-66 in beating cells and 90-99 in contractured cells. In contrast no significant difference was found in the metabolite levels in the three cellular states: (nmol per mg cell protein +/- S.E.M.) ATP, 20.9 +/- 1.5; CrP, 22.3 +/- 2.2; ADP, 6.03 +/- 0.67; Cr, 10.8 +/- 1. It is proposed that the combined action of myosine ATPase, ATP synthase and cytosolic and mitochondrial creatine kinases serves to buffer the metabolite levels during periods of enhanced oxygen consumption.
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PMID:High-energy phosphates in quiescent, beating and contracted cardiac cells. 326 May 16

The transmembrane potential (delta psi) of rabbit brain mitochondria was measured with the fluorescent dye dis--C2--5. During oxidative phosphorylation a fall in delta psi in the order of 20% was observed. In the presence of inhibitors of ATP synthesis, there was a good correlation between the fall in delta psi and the ADP-stimulated increase in respiration rate. The influence of endogenous calcium on the energetic metabolism of mitochondria was studied by measuring the changes of delta psi. An amount of 12 nmol Ca2+/mg protein cause half-inhibition of the ATP synthesis rate; 50 nmol/mg completely inhibits oxidative phosphorylation. The effect of the Ca2+ load on the ATPase activity of intact mitochondria was studied. It was found that endogenous calcium inhibits in a similar degree synthesis and hydrolysis of ATP. It was shown that both Ca ATP and Mg ATP can serve as a substrate for the mitochondrial ATPase.
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PMID:[Effect of Ca ions on the transmembrane electric potential, synthesis and hydrolysis of ATP in brain mitochondria]. 337 Feb 41

Two ATPase inhibitor proteins were isolated together from bovine heart mitochondria by a new procedure; each was purified further. The one inhibitor is a Ca2+-binding protein. It was found to contain 2 cysteine residues/mol as well as threonine and proline residues, all of which the other inhibitor (first isolated by Pullman and Monroy (Pullman, M.E., and Monroy, G. C. (1963) J. Biol. Chem. 238, 3762-3769] lacks. Its minimal molecular weight was 6390 with 62 amino acid residues/mol, and its isoelectric point was 4.6. Besides differences in size, composition, and response to Ca2+, the two inhibitor proteins also differed in response to sulfhydryl compounds, pH, KCl, and cardiolipin. Inhibition by the two inhibitor proteins was additive. Both cross-reacted with mitochondrial ATPase from rat skeletal muscle. Calmodulin, with or without Ca2+, had no effect on the activity of either inhibitor protein. Antibody to the Ca2+-binding inhibitor protein did not interact with the Pullman-Monroy inhibitor or have any effect on its activity. The antibody interacted with intact submitochondrial particles that contained both inhibitor proteins but not with particles from which only the Ca2+-binding inhibitor had been removed. Clearly, the two inhibitors are distinct immunologically as well as in other properties. The two types of inhibitor protein were also isolated from rat skeletal muscle mitochondria by the new procedure.
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PMID:The calcium-binding ATPase inhibitor protein from bovine heart mitochondria. Purification and properties. 340 40

The gap between early molecular evolution and the origin of the first cell may have been bridged by a photoheterotrophic obcell, consisting of genes and ribosomes attached to the outer surface of a phospholipid vesicle containing a light-driven proton pump and a proton-driven pyrophosphate synthase. I argue that the obcell was the substratum for the origin of DNA replication; DNA segregation by the growth and division of the peptidoglycan murein; periplasmic solute-binding proteins; bioenergetics, including the F0F1 proton-driven ATP synthase; active transport of calcium; and facilitated diffusion of nutrients across membranes, and that it played the major role in the replacement of ribozymes by protein catalysts. Curved growth of the peptidoglycan and a mutation causing septum formation produced the first true cell. Evolution of porins, sodium extrusion and potassium import, conversion of the facilitated diffusion proteins to active pumps, and the evolution of intermediary metabolism, carbon and nitrogen fixation, and of substrate level phosphorylation, completed the origin of the first negibacterial eubacterium, from which all other cells evolved, and from which they have inherited most of their major catalytic properties--with the notable exceptions of reverse transcriptase, RNA splicing, and methanogenesis, all of which I believe evolved very much later.
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PMID:The origin of cells: a symbiosis between genes, catalysts, and membranes. 345 90

The biochemical and functional changes associated with ligation (40 min) of the left circumflex coronary artery and subsequent reperfusion (60 min) in the rabbit made diabetic with alloxan were studied and compared with those of control animals. Measurement of haemodynamic parameters revealed that both left ventricular pressure and mean arterial pressure were significantly (P less than 0.05) decreased after ligation and reperfusion in the diabetic animals compared with controls. Analysis of subcellular organelle enzyme markers from the ischaemic tissue revealed that sarcolemmal Na+,K+-ATPase, mitochondrial ATPase and sarcoplasmic reticulum ATPase activities were decreased after ligation to the same extent in the diabetic and control animals. However, upon reperfusion, the recovery of mitochondrial ATPase activity was significantly (P less than 0.05) less in the diabetic animals than in the controls. Ion measurements revealed a significant (P less than 0.05) depletion of Mg in diabetic hearts before ligation, and this was augmented during reperfusion. In contrast, a significantly (P less than 0.05) higher calcium accumulation was observed upon reperfusion in the hearts of diabetic animals. Similarly, both tissue ATP levels and the ability of the mitochondria to generate ATP were depressed to a greater degree in the diabetic animals. Our results indicate, therefore, a greater susceptibility of the diabetic myocardium to ischaemic/reperfusion injury which in the clinical situation would exacerbate the problems associated with atherosclerosis and possibly contribute to the high mortality from cardiovascular complications in diabetic patients.
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PMID:Coronary artery ligation and reperfusion in rabbits made diabetic with alloxan. 381 32

A facile and high-yield synthesis of a new ATP analogue, 2-[(4-azido-2-nitrophenyl)amino]ethyl triphosphate (NANTP), is described. NANTP and ATP are hydrolyzed by skeletal myosin subfragment 1 (SF1) at comparable rates in the presence of Ca2+, Mg2+, or NH4+-EDTA. NANTP is also cleaved but less readily by mitochondrial F1-ATPase and by (Na+ + K+)-ATPase from dog brain and hog kidney. F-Actin markedly activates NANTP cleavage by SF1 in the presence of Mg2+, suggesting that the diphosphate product NANDP is slow to be released from the enzyme. [alpha-32P]NANDP binds to a single site on SF1 (KA = 1 X 10(6) M-1) with an affinity identical with that of ADP. The absorption maximum of NANDP was shifted from 474 to 467 nm upon binding to SF1, suggesting that the purine binding site has a dielectric constant of about 45. NANDP was trapped in nearly stoichiometric amounts at the active site by cross-linking SH1 and SH2 with N,N'-p-phenylenedimaleimide (pPDM) or by chelation with cobalt (III) phenanthroline [Wells, J., & Yount, R. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966]. The trapped [beta-32P]NANDP X SF1 complex, like the comparable ADP X SF1 complex, was stable for days at 0 degree C and could be purified free of extraneous analogue by ammonium sulfate precipitation and gel filtration. Photolysis of the purified complex gave greater than 50% covalent incorporation of the trapped NANDP into the 95-kilodalton (kDa) heavy chain of SF1. Limited trypsinization and analysis by gel electrophoresis showed that greater than 95% of the bound label was associated with the 25-kDa NH2-terminal peptide. Without trapping, NANDP labeling of SF1 was nonspecific and was not prevented by addition of a large excess of ATP. This new approach of trapping photoaffinity analogues by cross-linking agents before photolysis may prove to be of general usefulness in increasing the specificity and extent of labeling of enzymes that undergo substrate-induced conformation changes.
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PMID:2-[(4-Azido-2-nitrophenyl)amino]ethyl triphosphate, a novel chromophoric and photoaffinity analogue of ATP. Synthesis, characterization, and interaction with myosin subfragment 1. 407 91

Accumulation of calcium in the mitochondria of rat liver parenchymal cells at 16 and 24 hours after poisoning with carbon tetrachloride is associated with an increase in amount of liver inorganic phosphate, the persistence of mitochondrial adenosine triphosphatase activity, and the formation of electron-opaque intramitochondrial masses in cells with increased calcium contents. These masses, which form within the mitochondrial matrix adjacent to internal mitochondrial membranes, resemble those observed in isolated mitochondria which accumulate calcium and inorganic phosphate; are present in a locus similar to that of electron opacities which result from electron-histochemical determination of mitochondrial ATPase activity; and differ in both appearance and position from matrix granules of normal mitochondria. After poisoning, normal matrix granules disappear from mitochondria prior to their accumulation of calcium. As calcium-associated electron-opaque intramitochondrial masses increase in size, mitochondria degenerate in appearance. At the same time, cytoplasmic membrane systems of mid-zonal and centrilobular cells are disrupted by degranulation of the rough endoplasmic reticulum and the formation of labyrinthine tubular aggregates. The increase in amount of inorganic phosphate in rat liver following poisoning is balanced by a decreased amount of phosphoprotein. These chemical events do not appear to be related, however, as the inorganic phosphate accumulated is derived from serum inorganic phosphate.
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PMID:Liver parenchymal cell injury. 3. The nature of calcium--associated electron-opaque masses in rat liver mitochondria following poisoning with carbon tetrachloride. 428 48

On solubilization with Triton X-100 of sarcoplasmic reticulum vesicles isolated by differential centrifugation, the Ca2+-ATPase is selectively extracted while approximately half of the initial Mg2+-, or 'basal', ATPase remain in the Triton X-100 insoluble residue. The insoluble fraction, which does not contain the 100 000 dalton polypeptide of the Ca2+-ATPase, contains high levels of cytochrome c oxidase. Furthermore, its Mg2+-ATPase activity is inhibited by specific inhibitors of mitochondrial ATPase, indicating that the 'basal' ATPase separated from the Ca2+-ATPase by detergent extraction originates from mitochondrial contaminants. To minimize mitochondrial contamination, sarcoplasmic reticulum vesicles were fractionated by sedimentation in discontinuous sucrose density gradients into four fractions: heavy, intermediate and light, comprising among them 90-95% of the initial sarcoplasmic reticulum protein, and a very light fraction, which contains high levels of Mg2+-ATPase. Only the heavy, intermediate and light fractions originate from sarcoplasmic reticulum; the very light fraction is of surface membrane origin. Each fraction of sarcoplasmic reticulum origin was incubated with calcium phosphate in the presence of ATP and the loaded fractions were separated from the unloaded fractions by sedimentation in discontinuous sucrose density gradients. It was found that vesicles from the intermediate fraction had, after loading, minimal amounts of mitochondrial and surface membrane contamination, and displayed little or no Ca2+-independent basal ATPase activity. This shows conclusively that the basal ATPase is not an intrinsic enzymatic activity of the sarcoplasmic reticulum membrane, but probably originates from variable amounts of mitochondrial and surface membrane contamination in sarcoplasmic reticulum preparations isolated by conventional procedures.
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PMID:Highly purified sarcoplasmic reticulum vesicles are devoid of Ca2+-independent ('basal') ATPase activity. 610 77

Low concentrations of ACTH, 7 x 10(-12) M, caused a marked stimulation of the 100,000 x g particulate guanylate cyclase without any detectable change in the adenylate cyclase activity. The lowest concentration of the hormone that elicited adenylate cyclase stimulation was 7 x 10(-10) M, a concentration 100--fold higher than that required to stimulate the guanylate cyclase. Although calcium was found to be obligatory in the hormonally--dependent guanylate cyclase activity, calcium alone could not duplicate the ACTH effect. Sodium nitroprusside and ascorbic acid inhibited the particulate guanylate cyclase activity. While ACTH was unable to stimulate the soluble guanylate cyclase, sodium nitroprusside markedly stimulated this enzyme. From these data, we conclude that the adrenal guanylate cyclase exists in two forms, particulate and soluble. The particulate form is specifically responsive to ACTH, and calcium is one of the essential coupling factors of this hormonally--responsive guanylate cyclase.
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PMID:Adrenocorticotropic hormone-responsive guanylate cyclase in the particulate fraction of rat adrenal glands. 611 49

A mechanism is proposed for the coupling between ion transport and enzyme catalysis. The basic concept is that enzymes associated with transport exist in two possible conformations. Each conformation has the potential of catalyzing the enzymatic reaction, and pumping is associated with the conversion of one conformational form to the other. The conformational transition is triggered by the kinetic blockage of specific mechanistic steps for each conformation. Such blockages can cause a cycling between the two conformations concomitant with catalysis. This mechanistic concept is consistent with a variety of results obtained with the Na+,K+-ATPase, the Ca2+,Mg2+-ATPase, and ATP synthesizing enzymes (coupling factors).
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PMID:Unifying concept for the coupling between ion pumping and ATP hydrolysis or synthesis. 612 23


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