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Query: UNIPROT:Q8N5D0 (ADP)
 37,930 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of sarcomere length and stretching on the tension and the rate of ATP splitting was studied using small fiber bundles from glycerinated rabbit psoas muscle. The rate of ATP slitting was determined by measuring ADP production, while the tension development in response to a contracting solution (at pCa 5.3) was recorded in the same preparation. The isometric tension developed by the preparation decreased when the sarcomere length was increased. The decrease of tension development was accompanied by a decrease in the rate of ATP splitting. If a preparation exerting steady isometric tension was stretched by 5--10% at a velocity of 0.1 mm/s, the rate of ATP splitting was increased after stretching, while the steady isometric tension attained after stretching was also higher than the initial value. The extent of the excess ATP splitting caused by stretching decreased with increasing sarcomere length. These results suggest that the rate of the interaction cycle between actin and myosin molecules may increase as a result of stretching.
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PMID:The effect of sarcomere length and stretching on the rate of ATP splitting in glycerinated rabbit psoas muscle fibers. 16 Apr 18

The kinetic parameters of the inhibition of monovalent cation activated myosin ATPase by ADP were investigated. The inhibitor constant (KI) was 1.65 X 10(-4) M and the maximal velocity (V) was 1.28 mumol Pi/mg myosin/min in the presence of 0.3M Kcl at 20 degrees C. The dependence of 1/VO on inhibitor concentration and the pH dependence of KI and Km (i.e. pKi approximately equal to pKm) show that the inhibition has a pure competitive character. The results are supported by energetic parameters, too. The enthalpy of the formation of (EI) complex was calculated. Similar results were obtained also in the presence of Rb+ activated myosin ATPase and subfragment-I K+ ATPase.
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PMID:Kinetic study of the inhibition of myosin ATPase activity by ADP. 16 61

The effect of temperature on ESR spectra of spin-labelled myosin and myosin-ADP complex was studied. It was shown that mobility of the sptrongly immobilized spin label almost did not change with temperature (-2 degrees C-37 degrees C) whereas mobility of the slightly immobilized spin label changed in a complicated manner and not monotonously. The observed changes in mobility of the slightly immobilized spin label and characteristics of the ESP spectrum of the myosin-ADP complex suggest that temperature causes continuous changes of the structure in the local environment of the binding sites of the spin label, and on the average, one conformation of myosin and myosin-ADP complex molecules exists at any temperature.
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PMID:[Temperature dependence of the epr spectra of a spin-labeled myosin and its complex with adp]. 16 6

1. Procedures are given for the syntheses of alpha,omega-dinucleoside 5'-polyphosphates as inhibitors of adenylate kinases. The following order for the ability of inhibiting pig muscle adenylate kinase was observed: Ap5A greater than 1:N6-etheno-Ap5A greater than Ap6A greater than Gp5A greater than Ap4A greater than Up5A. The synthesis of adenosine tetraphosphate, the starting material for Ap5A, is also described. 2. One molecule of pig muscle adenylate kinase binds one molecule of Ap5A. The difference spectrum of Ap5A-adenylate kinase with its maximum of 5050 M-1 - cm-1 at 271 nm, as well as the fluorescence properties of 1:N6-etheno-Ap5A can be used for kinetic and binding studies. 3. The specific binding of the negatively charged Ap5A was exploited in the preparation of human muscle adenylate kinase. The enzyme was purified to homogeneity with an overall yield of 65%, the absolute value being 70 mg per kg of muscle. 4. The effect of Ap5A on adenylate kinase in extracts of various cells and cell organelles was tested. A ratio of 1:50 (mol/mol) for Ap5A to other nucleotides was used for suppressing the adenylate kinase activity in extracts of mammalian and insect skeletal muscel, of human erythrocytes and of Staphylococcus aureus. A ratio of 1:5 was found to be necessary for the adenylate kinase from tobacco leaves and spinach chloroplasts, and a ratio of 2:1 was needed for suppressing the adenylate kinase from bovine liver mitochondria, human kidney homogenate and from Escherichia coli. Ap5A appears not to be metabolized in any of the above extracts. These results indicate that Ap5A can be used for evaluating the contribution of adenylate kinase to the production of ATP fro ADP in energy-transducing systems. 5. Contaminating adenylate kinase can be inhibited by a concentration of Ap5A which does not interfere in the study of many (phospho)kinases and ATPases. The applications of Ap5A in the assay for nucleoside diphosphokinase and in the study of mechanical and biochemical properties of contractile proteins are representative examples. The use of Ap5A makes it possible to study the effect of ADP per se in such systems. 6. Sepharose-bound Ap5A was used for removing traces of adenylate kinase from samples of myosin and creatine kinase. 7. In the presence of Ap5A the activity of creatine kinase was measured in hemolytic serum of venous blood, in plasma of capillary blood and in samples of whole blood after complete hemolysis had been induced. The clinical significance of these findings are shown for cases of myocardial infarction and muscular dystrophy.
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PMID:Synthetic inhibitors of adenylate kinases in the assays for ATPases and phosphokinases. 17 Jan 10

From transient kinetic studies of the Mg2+-dependent adenosine triphosphatase of myosin subfragment 1, prepared from rabbit skeletal muscle, a seven-step mechanism has been proposed. Features of this mechanism include two-step processes for ATP and ADP binding in which the binary complex isomerizes in addition to a rapid nucleotide association step. In the case of ATP a large negative standard free energy change is associated with the isomerization. An overall rate-limiting isomerization of the myosin-product complex prior to product release has been identified. Studies on the mechanism of cleavage of ATP bound to the active site indicate the process is readily reversible and can account for the observation that more than one oxygen of the product phosphate arises from water. This proposal has been substantiated by the finding that the oxygen atoms of the gamma-phosphoryl group of bound ATP also undergo extensive exchange with water.
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PMID:Transient kinetic and isotopic tracer studies of the myosin adenosine triphosphatase reaction. 17 37

The effect of substrate on the far UV (185-250 nm) and near UV (250-325 nm) circular dichroism (CD) of myosin and heavy meromyosin (HMM) was studied. The following results were obtained with the addition of ATP (during various conditions of hydrolysis), ADP, and pyrophosphate: (1) no changes were observed in the far UV CD, (2) ATP and ADP perturbed the near UV CD only at spectral regions below 280 nm coinciding with the regions of their optical activity, (3) the optically inactive pyrophosphate caused no change in the near UV CD, and (4) myosin and HMM gave exactly the same results. These results suggest that myosin-substrate interaction in vitro does not result in a delocalized conformational change.
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PMID:Does myosin-substrate interaction in vitro result in a delocalized conformation change? 17 27

The triphosphate ester of tubercidin (tubercidin triphosphate, TuTP) was synthesized. This is an analog of ATP in which a CH group replaces the N-7 of the adenine ring. The rate of TuTP hydrolysis by myosin in the presence of Mg2+ was the same as that of ATP in the 10(-7)-10(-3) M range, whereas the increment in the optical density of myosin ihe 290mmu region caused by TuTP was twice that caused by ATP. TuTP is hydrolyzed by actomyosin faster than ATP, the value of Vmax being about 4 times larger while the Km values were of the same order of magnitude. The rate of superprecipitation induced by TuTP was 50% of that caused by ATP at nucleotide concentrations of 3-60 muM. A similar difference was observed with respect to the rate of tension development by glycerol-extracted rabbit psoas fibers upon addition of these two substances. Substitution of ADP by tubercidin diphosphate (TuDP) in F-actin did not affect the rate of superprecipitation or enzymic activity of actomyosin.
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PMID:A study on the reactions of tubercidin triphosphate with myosin and actomyosin. 17 23

The chemical synthesis of adenosine 5'-(O-1-thiotriphosphate) (ATPalphaS) and adenosine 5'-(O-2-thiotriphosphate) (ATPbetaS) is described. Both exist as a pair of diastereomers, A and B. The isomers of ATPalphaS can be distinguished on the basis of their different reaction rates with myokinase as well as nucleoside diphosphate kinase. With both enzymes, isomer A reacts fast whereas isomer B reacts considerably more slowly. Phosphorylation of a mixture of isomers of ADPalphaS with pyruvate or acetate kinase yields ATPalphaS, isomer A, whereas the phosphoryl transfer with creatine or arginine kinase yields isomer B. The isomers of ATPbetaS differ in their reactivity with myosin. Isomer A is readily hydrolyzed, whereas isomer B is not. However, isomer B reacts faster with nucleoside diphosphate kinase and ADP than isomer A. Phosphoryl transfer with pyruvate kinase onto ADPbetaS yields ATPbetaS, isomer A, with acetate kinase, isomer B.
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PMID:Synthesis and properties of diastereoisomers of adenosine 5'-(O-1-thiotriphosphate) and adenosine 5'-(O-2-thiotriphosphate). 17 53

Electron paramagnetic resonance spectroscopy and water proton relaxation rate (PRR) measurements were used to characterize a complex formed at the myosin subfragment 1 (S1) ATPase site with stoichiometric amounts of Mn(II) and ADP. In the absence of nucleotide, Mn(II) binding at the active site is very weak, although two other classes of sites for Mn(II) on subfragment 1 were identified which are not directly involved in the ATPase reaction. A high affinity Mn(II) site (termed L-site with KL = 3 muM) is associated with a region of the molecule which is susceptible to proteolysis (probably the LC2 light chain subunit) since its stoichiometry depends on the conditions employed for the preparation of subfragment 1 during the papain treatment of myosin. In addition there are a number of weak sites for Mn(II) (termed N-sites) probably associated with anionic groups on the surface of the molecule. In order to study the properties of Mn(II) and ADP bound at the active site by magnetic resonance techniques, subfragment 1 preparations virtually free of the L-site were used, since such an ancillary site competes for the available Mn(II). MnADP binds to subfragment 1 with an apparent dissociation constant, KT, of about 4 muM at 25 degrees. The resultant complex, S1-MnADP, has a low PRR enhancement factor (1.7 at 24.3 MHZ), and its frequency (magnetic field) dependence indicates that this is because there are no readily exchangeable water molecules within the first coordination sphere of Mn(II. Relaxation of the bulk solvent is mediated by protons bound transiently within the outer spheres (4 to 7 A) of the Mn(II). A nitroxide spin label attached to the reactive thiol group of subfragment 1 enhances the solvent PRR, and this property is sensitive to the binding of MgADP to the active site. However, no dipolar spin-spin interaction was detected between the nitroxide group and Mn(II) in the S1-MnADP complex, indicating that the metal ion and thiol group are well separated.
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PMID:Investigations of equilibrium complexes of myoxin subfragment 1 with the manganous ion and adenosine diphosphate using magnetic resonance techniques. 17 50

It is shown that three types of ESR spectra of myosin labeled with both acetate and acetamide spin labels are distinguished. These three types are the spectrum of initial preparation, myosin--ADP complex spectrum and the spectrum recorded during ATP hydrolysis. The ESR spectra of myosin labeled with acetate spin label are more sensitive to conformational changes of myosin induced by complex formation and temperature.
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PMID:[Study of conformational transitions in myosin using 2 types of spin label]. 18 36


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