3H]adenosine triphosphate: release during stimulation of enteric nerves

The isolated taenia coli of the guinea pig takes up tritiated adenosine, adenosine monophosphate, adenosine diphosphate, and adenosine triphosphate, in preference to tritiated inosine and adenine. After uptake, [(3)H]adenosine is converted and retained primarily as [(3)H]adenosine triphosphate. Tritium is released from taenia coli treated with [(3)H]adenosine upon activation of the nonadrenergic inhibitory nerves. These results are consistent with the previous evidence that adenosine triphosphate may be the transmitter from the nerves.     

Brain adenosine triphosphate: decreased concentration precedes convulsions

The concentration of adenosine triphosphate in the brain decreased before the onset of generalized convulsions in unanesthetized rats subjected to acute hypoxia or treated with hydroxylamine or pentylenetetrazole (Metrazol). As the convulsive episode continued, adenosine triphosphate decreased further. Stimulation of adenosine triphosphate production forestalled its disappearance from the brain and delayed the development of seizure activity.     

Mercurial-induced transformation of myosin prevented by adenosine triphosphate and pyrophosphate

Adenosine triphosphate and pyrophosphate prevent the loss of Ca(//)-activated adenosine triphosphatase activity caused by high concentrations of mercurial sulfhydryl reagent. They concomitantly prevent the transformation of myosin into faster-sedimenting products. This is adduced as support for the hypothesis that the strategic sulfhydryl group is not binding adenosine triphosphate at the active site, but is initiating a conformational change upon its reaction with the mercurial reagent.     

Glycerinated muscle fibers: relation between isometric tension and adenosine triphosphate hydrolysis

The isometric tension of glycerinated muscle fibers and the adenosine triphosphatase activity of homogenates were determined as a function of the concentration of adenosine triphosphate without the addition of divalent cations. These two phenomena are not parallel; large tensions can be developed with negligible hydrolysis of adenosine triphosphate. It is concluded that the large negative free energy change of the hydrolysis is not required for shortening or development of tension.     

Adenosine triphosphate usage by flagella

Comparison of beat frequencies with rates of dephosphorylation of adenosine triphosphate by glycerinated sea urchin spermatozoa as functions of adenosine triphosphate concentration suggests that each molecule of the flagellar adenosine triphosphatase, dynein, dephosphorylates one adenosine triphosphate molecule during each beat cycle.     

Group I intron self-splicing with adenosine: evidence for a single nucleoside-binding site

For self-splicing of Tetrahymena ribosomal RNA precursor, guanosine binding is required for 5' splice-site cleavage and exon ligation. Whether these two reactions use the same or different guanosine-binding sites has been debated. A double mutation in a previously identified guanosine-binding site within the intron resulted in preference for adenosine (or adenosine triphosphate) as the substrate for cleavage at the 5' splice site. However, splicing was blocked in the exon ligation step. Blockage was reversed by a change from guanine to adenine at the 3' splice site. These results indicate that a single determinant specifies nucleoside binding for both steps of splicing. Furthermore, it suggests that RNA could form an active site specific for adenosine triphosphate.     

Cyclization of the phosphate side chain of adenosine triphosphate: formation of monoadenosine 5'-trimetaphosphate

Monoadenosine 5'-trimetaphosphate has been prepared from adeno-sine 5'-triphosphate by a carbodiimide-mediated condensation. The molecule was characterized by (3l)P nuclear magnetic resonance, and its (31)P spectrum was simulated through the assumption of a three-phosphorus spin system. The molecule is highly reactive and is rapidly converted to adenosine triphosphate upon contact with water.     

A fluorescent modification of adenosine triphosphate with activity in enzyme systems: 1,N 6 -ethenoadenosine triphosphate

A new, highly fluorescent adenosine triphophate (ATP) analog, 1,N(6) ethenoadenosine triphosphate, has been synthesized. Its fluorescence properties, including the long fluorescence lifetime and the possibility of detection at very low concentrations, in conjunction with its activity in the representative enzyme systems here reported, make it a valuable probe of enzymic mechanism and structure.     

Micelle formation between 5-hydroxytryptamine and adenosine triphosphate in platelet storage organelles

As judged by analytical ultracentrifugation, 5-hydroxytryptamine and adenosine-5'-triphosphate form micelles in artificial mixtures and also in storage organelles containing 5-hydroxytryptamine of blood platelets of rabbits. Their average apparent molecular weights depend on the concentration and on the molar ratio of the two constituents. The 5-hydroxytryptamine and adenosine triphosphate of these 5-hydroxytryptamine organelles may be stored in vivo together as micelles with apparent molecular weights of several hundred thousands or more.     

Adenosine triphosphate synthesis coupled to K+ influx in mitochondria

The influx of K+ into swollen mitochondria in the presence of valinomycin results in the synthesis of adenosine triphosphate in which approximately one H+ disappears per adenosine triphosphate synthesized. The synthesis is blocked by atractyloside but is insensitive to oligomycin and relatively insensitive to uncouplers.     

Tritiated digoxin binding to (Na+ + K+)-activated adenosine triphosphatase: possible allosteric site

Tritiated H(3)-digoxin specifically binds to a cardiac (Na(+) + K(+))-activated adenosine triphosphatase. In the presence of adenosine triphosphate and other nucleoside di- and triphosphates, binding is stimulated by sodium ion, the apparent rate constant being similar to that reported for phosphorus-32 incorporation from adenosine triphosphate and for the adenosine triphosphatase activity. In the presence of magnesium, manganese, inorganic phosphate, or other ions, sodium ion inhibits binding. The data support an allosteric type of sodium-potassium ion pump.     

Aspirin: its effect on platelet glycolysis and release of adenosine diphosphate

Incubation of human platelets with aspirin inhibited glycolysis and produced a fall in the concentration of adenosine triphosphate. When platelets were exposed to collagen there was an increase in glycolysis and release of adenosine diphosphate. Prior incubation of the platelets with aspirin for 5 minutes did not totally suppress the increase in glycolysis after exposure to collagen but completely inhibited the collagen-induced reaction of the release of adenosine diphosphate. It is suggested that aspirin acts on human platelets by inhibiting both release of adenosine diphosphate and the transport of glucose across the platelet membrane.     

Oxygen consumption and cellular ion transport: evidence for adenosine triphosphate to O2 ratio near 6 in intact cell

Oxygen (O2) consumption and net K+ uptake were measured simultaneously upon reintroduction of K+ into a K+-depleted suspension of renal tubules. The K+/O2 stoichiometries of 11.8 +/- 0.2 and 8.4 +/- 0.6 were obtained for reduced nicotinamide adenine dinucleotide- and flavoprotein-linked substrates, respectively. These values complement classical K+ to adenosine triphosphate (ATP) and ATP/O2 stoichiometries, thereby demonstrating a remarkably efficient coupling between the processes of Na+- and K+-dependent adenosinetriphosphatase-mediated ion transport and oxidative phosphorylation within the intact cell.     

Nucleoside triphosphate termini from RNA synthesized in vivo by Escherichia coli

Alkaline hydrolyzates of RNA made in vivo by Escherichia coli contain ribonucleoside-3'-monophosphate-5'-triphosphates. These probably arise by hydrolysis of the initial nucleoside triphosphate from the 5' terminus of the nascent RNA chains. Logarithmically growing cultures, labeled for 45 seconds with (32)P-labeled phosphate, yield about 2000 molecules of labeled tetraphosphate per cell, this yield increasing only slightly with continued labeling. Only the tetraphosphates of adenosine and guanosine have been found in Escherichia coli, and these two are present in approximately equal amounts.     

Adenosine triphosphate: protection against radiation-indued chromosome loss in Drosophila

Injection of 5 milligrams of adenosine triphosphate per milliliter into adult Drosophila melanogaster X(e2) yB/sc(8) y(+) 4 to 8 hours old either immediately before or after administration of 2000 roentgens of x-rays protected those cells in spermatogenesis which were in or near meiosis from the loss of the ring X or the y(+) portion of Y chromosome. The loss of the chromosomes was determined by appearance of exceptional XO males in the offspring.     

Normalization of depressed heart function in rats by ribose

Severe constriction of the abdominal aorta and simultaneous injection of isoproterenol in rats induced depression in heart function and reductions in cardiac adenosine triphosphate and total adenine nucleotides. When ribose was continuously infused for 24 hours, biosynthesis of cardiac adenine nucleotides was stimulated to such an extent that the reductions in adenosine triphosphate and total adenine nucleotides were prevented and left ventricular hemodynamic parameters were normal. These results support the hypothesis that adenosine triphosphate is primarily responsible for depression in myocardial contractility and that ribose is cardioprotective through its pronounced effects on adenine nucleotide metabolism in heart muscle.     

Adenosine 3',5'-monophosphate: regional differences in chick embryos at the head process stage

The concentrations of adenosine 3',5'-monophosphate and adenosine triphosphate and the activity of phosphodiesterase were determined in different regions of chick embryos at the head process stage. Adenosine 3',5'-monophosphate, adenosine triphosphate, and phosphodiesterase were estimated to be higher in the mesoderm-forming portions of the hypoblast than in portions that form neural structures from Hensen's node or the epiblast.     

Crystal structure of the catalytic subunit of cyclic adenosine monophosphate-dependent protein kinase

The crystal structure of the catalytic subunit of cyclic adenosine monophosphate-dependent protein kinase complexed with a 20-amino acid substrate analog inhibitor has been solved and partially refined at 2.7 A resolution to an R factor of 0.212. The magnesium adenosine triphosphate (MgATP) binding site was located by difference Fourier synthesis. The enzyme structure is bilobal with a deep cleft between the lobes. The cleft is filled by MgATP and a portion of the inhibitor peptide. The smaller lobe, consisting mostly of amino-terminal sequence, is associated with nucleotide binding, and its largely antiparallel beta sheet architecture constitutes an unusual nucleotide binding motif. The larger lobe is dominated by helical structure with a single beta sheet at the domain interface. This lobe is primarily involved in peptide binding and catalysis. Residues 40 through 280 constitute a conserved catalytic core that is shared by more than 100 protein kinases. Most of the invariant amino acids in this conserved catalytic core are clustered at the sites of nucleotide binding and catalysis.     

Renal concentrating mechanism: possible role for sodium-potassium activated adenosine triphosphatase

Sodium-potassium activated adenosine triphosphatase activity was found to be almost twice as high in renal medulla as in cortex. Infusion of digoxin, a specific inhibitor of the enzyme, into one renal artery of the dog resulted in unilateral natriuresis, impaired concentrating capacity, and reduction of the enzyme activity in both cortex and medulla. It is suggested that the sodium-potassium adenosine triphosphatase plays an important role in urine concentration mechanisms.     

Cyclic adenosine monphosphate, metabolites, and phosphorylase in neural tissue: a comparison a methods of fixation

Fixation of rat brain tissue by freeze-blowing, microwave irradiation, immersion of whole rats in liquid nitrogen, and decapitation into liquid nitrogen indicates that postmortem changes in metabolites and enzyme forms are minimal in freeze-blown brains. Cyclic adenosine monophosphate levels are lowest in microwave-irradiated brains, which has been interpreted by some investigators to indicate rapid fixation and minimal anoxia. However, the changes in phosphocreatine, adenosine triphosphate, lactate, and phosphorylase clearly demonstrate that fixation by freeze-blowing or immersion in liquid nitrogen more closely approximate the state in vivo.