Evidence for Interaction Between Magnesium and Purine or Pyrimidine Rings of 5'-Ribonucleotides

Hotta, Ken; Brahms, J.; Morales, Manuel F.

doi:10.1021/ja01465a059

Cited by 34 publications

(10 citation statements)

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“…Thus, it is seen that there is a satisfactory closeness of the pK and D r H m values in six of the possible nine comparisons that can be made. While, we cannot explain the differences seen for the reactions involving H 3 IMP(aq), MgH 2 IDP(aq), and H 3 ITP 2À (aq), we shall proceed with our calculations by using the relatively well established pK and D r H m values for the adenosine 5 0 -phosphate series [25].…”

Section: Thermochemical Pathway Calculationsmentioning

confidence: 99%

“…b Based on values of pK and D r H m selected by Martell et al [22]. e Based on pK = 3.76 at I = 0.05 mol AE dm À3 reported by Hotta et al [25]. The temperature is assumed to be 298.…”

Section: Thermochemical Pathway Calculationsmentioning

confidence: 99%

“…15 Specifically, D r H m ¼ 0.9 kJ Á mol À1 and D r G m ¼ À13.0 kJ Á mol À1 for reaction (40) and D r H m ¼ 1.7 kJ Á mol À1 and D r G m ¼ À12.6 kJ Á mol À1 for reaction (15). Thus, we shall assume the values of D r H m and D r G m for reactions (16) and (17) in table 4 are the same as the corresponding reactions involving the adenosine 5 0 -phosphates [25], with the exception of reaction (15) where we shall use the results of the direct study [18].…”

Section: Thermochemical Pathway Calculationsmentioning

confidence: 99%

“…TABLE 7 Standard molar transformed enthalpies of formation D f H 0 m and standard molar transformed Gibbs free energies of formation D f G 0 m for the aqueous biochemical reactants inosine, IMP (inosine 5 0 -monophosphate), IDP (inosine 5 0 -diphosphate), and ITP (inosine 5 0 -triphosphate) at the temperature T = 298.15 K, pH = 7.0, pMg = 3.0, and the ionic strength I m = 0. 25 …”

Section: Thermochemical Pathway Calculationsmentioning

confidence: 99%

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Thermochemistry of inosine

Boerio‐Goates

Hopkins

Monteiro

et al. 2005

The Journal of Chemical Thermodynamics

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Section: Thermochemical Pathway Calculationsmentioning

confidence: 99%

“…b Based on values of pK and D r H m selected by Martell et al [22]. e Based on pK = 3.76 at I = 0.05 mol AE dm À3 reported by Hotta et al [25]. The temperature is assumed to be 298.…”

Section: Thermochemical Pathway Calculationsmentioning

confidence: 99%

Section: Thermochemical Pathway Calculationsmentioning

confidence: 99%

Section: Thermochemical Pathway Calculationsmentioning

confidence: 99%

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Thermochemistry of inosine

Boerio‐Goates

Hopkins

Monteiro

et al. 2005

The Journal of Chemical Thermodynamics

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“…According to Blum, this ringenzyme interaction retards the desorption of the diphosphate following P-O-P hydrolysis, thus effecting an inhibition of what would be the activity in the absence of interaction. Gilmour3' has additionally assumed that this retarding interaction is pH sensitive and maximal at pH [7][8] (3.5) of the G-actin concentration, and that the addition of F-actin causes a burst of ATP splitting. To provide a structural basis for the polymerization and ATPase effects, Oosawa is now proposing a helical (rather than linear, to account for interactive effects), possibly salt-linked, and rather delicate structure for F-actin.…”

Section: Specific Sulfhydryl Reagentsmentioning

confidence: 99%

The ATPases of Muscle Proteins

1961

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The ideas and results of Blum, Oosawa, Strohman, and many others are reviewed and, when consolidated with the authors' work, lead to the following picture of muscle protein adenosine triphosphatases (ATPases). Two major features of imiyocin ATPase seem to be a catalytic interaction between enzyme, a metal cation, and the terminal pyrophosphate moiety of adenosine triphosphate (ATP) and a rate-retarding interaction between enzyme, Mg++, and the purine ring of ATP. Sulfhydryl groups of the enzyme participate at both loci. In the catalytic interaction anl ionizable group (pK, ca. 6.8) may participate. G-actiin molecules binding ATP (probably by the purine ring) and relieved of their mutual repulsion cooperate in catalysing dephosphorylation, possibly helical, structure of F-actin.IN CONTRIBUTING to this symposium we are tacitly assuming that, as regards our subject, there is no substantial difference between heart and skeletal muscle tissue. It has also to be said that, although ATPases are emphasized in the title and in the paper itself, it is very possible, in view of work such as Strohman's,1 that in situ one or more of these enzymes function in phosphate transfer rather than in ATP hydrolysis. Such a possibility would not vitiate the merit of ATPase studies, since the objectives in most of these studies are clues about enzyme surfaces and enzyme-substrate interactions. For these purposes it is quite legitimate to consider various "acceptors," among them water. At the same time, we must acknowledge that, even if these studies were totally successful and we understood precisely the mechanisms of the enzymes, we would still have to integrate our information with that of other speakers in order to understand how muscle "works."In this paper we shall consider primarily the ATPase activities of myosin and actin, but first it is convenient to touch upon some properties of ATP and its relatives. SubstratesFor the enzymes to be considered, the "natural" substrate appears to be adenosine triphosphate (ATP). A long-known property of ATP is that its free energy of hydrolysis is substantial. A possible consequence of this fact for interactions of ATP with its enzymes is the plausibility of formation of energetically costly enzyme intermediates. Other conceivable properties of ATP as a substrate, such as charge and binding affinities of its various moieties, have generally received scant attention. In recent years, however, interest in ATP-metal cation complexes has been kindled by mounting evidence that metal cations play a critical role in ATPase and contractile properties.It is safe to assume that metal cations are chelated by the polyphosphate end of ATP and may form a sort of electrostatic "cement " linking substrate to enzyme and facilitating distal hydrolytic attack by water molecules. However, enzymologic investigations have prompted speculation that metal cations also interact with the ring end of ATP, either to anchor it to enzyme or to its own polyphosphate end. The existence of these interactions can be and has ...

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Complexes of silver ion with natural and synthetic polynucleotides

1966

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SynopsisA study of silver-ion binding by nucleic acids and synthetic ribo and deoxyribopolynucleotides, has been carried out by means of potentiometric titration, thermal transition, and difference spectra. It is clearly demonstrated that a strong complex between Ag+ and nitrogen atoms of bases is made reversibly. Binding constants and site numbers are determined for each type of polynucleotide. Base reactivity varies strongly with chain length, and a cooperative phenomenon is found in each case. Two successive complexes with DNA are seen in all the three techniques, and they have the same characteristics as complexes with respectively poly-dGC and poly dAT. In the first complex, Ag+ is linked to four bases, provided two of them are a G-C pair. Calculated and experimental values of site numbers agree very well for DNA of different G-C content. Thermal stabilization occurs simultaneously, and the increase of melting temperature corresponds to calculated changes of stacking energy between base pairs. In the second complex a new ordered structure insensitive to temperature is formed, with simultaneous release of protons. The stoichiometry can be related to base sequence. Complexing with silver increases the resistance of TMV RNA to both temperature and ribonuclease; a tentative explanation is given in the latter case.* Present address: Centre de Recherches sur lea Macromol6cules, Strasbourg, France. 51 52DAUNE, DEKKER, AND SCIIACHMAN d i s p e r s i~n . '~-~~ The role of bases and particularly of amino groups and nitrogen atoms is definitely established but as yet the mechanism remains unknown. l9 Singer and Fraenkel-Conrat20 have shown that several transition metals are able to protect viral RNA against RNase, without changing the properties of the enzyme. As a result of this finding, it seemed of interest to examine in detail the interaction of silver ions with RNA in terms of possible changes in the configuration of the macromolecules. Early in the work it became evident that this type of study had to be extended to several natural and synthetic polynucleotides in order to provide various models for the interpretation of data. EXPERIMENTAL MaterialsTMV RNA was extracted from the virus by the classical phenol method. Stock solutions in water at concentrations of 2-7 mg./ml. were kept frozen at -20°C. Under these conditions there was no loss of infectivity over several months. The same type of storage was used for all the other solutions of polynucleotides except for DNA, which was always maintained in anionic strength of at least 10-3M.Soluble RNA (s-RNA) was isolated from wheat germ according to the method of Lane and A1len2l and purified further by DEAE column chromatography.DNA was a sample extracted from calf thymus and donated by N. Simmons.

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Evidence for Interaction Between Magnesium and Purine or Pyrimidine Rings of 5'-Ribonucleotides

Cited by 34 publications

References 0 publications

Thermochemistry of inosine

Thermochemistry of inosine

The ATPases of Muscle Proteins

Complexes of silver ion with natural and synthetic polynucleotides

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