Proton and vanadium-51 NMR investigation of the complexes formed between vanadate and nucleosides

Tracey, Alan S.; Leon-Lai, Chui Har

doi:10.1021/ic00016a018

Cited by 35 publications

(36 citation statements)

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“…In view of the results obtained with the other peptides this curvature was attributed to non-ideal behaviour in solution, a result perhaps of attractive interactions between the hydrocarbon rings of different proline entities. Similar observations have been ascribed to based stacking interactions in the nucleoside/vanadate systems (15).…”

Section: Methodssupporting

confidence: 77%

Stereochemical requirements for the formation of vanadate complexes with peptides

Jaswal¹,

Tracey²

1991

Can. J. Chem.

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The condensation reactions occurring between vanadate and a number of amino aiids and simple peptides have been studied by 51V nuclear magnetic resonance. Vanadate and ligand stoichiometry has been established for the complexes formed and their formation constants determined. The amino acids were all found to undergo rather weak interactions with vanadate and in general provided two products with 51V chemical shifts near -545 and -555 ppm. The peptides also gave minor products with NMR signals occurring with that of vanadate itself. However, in this case, the major products occur at approximately -510 ppm. These latter complexes are monovanadate, monoligand complexes which require the terminal amino, the carboxylate groups and an unsubstituted nitrogen in the peptide linkage in order for product formation to occur. Sidechains promote product formation, apparently by favouring a more readily complexed peptide conformation. Formation constants vary from about 20 to 50 M-' depending on the sidechain. The carboxylate group can be replaced by a hydroxymethyl. This, however, leads to a significant decrease in product formation at pH 7. Hydrogen ion concentration studies showed that the complexes, when considered to be formed from VO4H2-and neutral peptide, did not require or give off protons. However, when the carboxylate was replaced by the alcohol functionality a proton was released. On the basis of this study the coordination of the vanadatelpeptide complexes has been assigned.

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Section: Methodssupporting

confidence: 77%

Stereochemical requirements for the formation of vanadate complexes with peptides

Jaswal¹,

Tracey²

1991

Can. J. Chem.

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“…40 The formation constant for U>v has been estimated to be (1.8 ± 1.5) M −1 at pH 7. 42 The value estimated for the cyclic tetrahedral complex (i.e., U>v minus H 2 O) is (4.5 ± 1.1) M −1 . In addition, acyclic 1:1 nucleoside:vanadate complexes may occur at low levels.…”

Section: What Is the Value Of K I For Uridine 2′3′-cyclic Vanadate?mentioning

confidence: 94%

Pentavalent Organo-Vanadates as Transition State Analogues for Phosphoryl Transfer Reactions

Messmore

Raines

2000

J. Am. Chem. Soc.

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Pentavalent organo-vanadates have been put forth as transition state analogues for a variety of phosphoryl transfer reactions. In particular, uridine 2′,3′-cyclic vanadate (U>v) has been proposed to resemble the transition state during catalysis by ribonuclease A (RNase A). Here, this hypothesis is tested. Lys41 of RNase A is known to donate a hydrogen bond to a nonbridging phosphoryl oxygen in the transition state during catalysis. Site-directed mutagenesis and semisynthesis were used to create enzymes with natural and nonnatural amino acid residues at position 41. These variants differ by 10 5 -fold in their k cat /K m values for catalysis, but <40-fold in their K i values for inhibition of catalysis by U>v. Plots of logK i vs log(K m /k cat ) for three distinct substrates [poly(cytidylic acid), uridine 3′-(p-nitrophenyl phosphate), and cytidine 2′,3′-cyclic phosphate] have slopes that range from 0.25 and 0.36. These plots would have a slope of unity if U>v were a perfect transition state analogue. Values of K i for U>v correlate weakly with the equilibrium dissociation constant for the enzymic complexes with substrate or product, indicating that U>v bears some resemblance to the substrate and product as well as the transition state. Thus, U>v is a transition state analogue for RNase A, but only a marginal one. This finding indicates that a pentavalent organo-vanadate cannot necessarily be the basis for a rigorous analysis of the transition state for a phosphoryl transfer reaction.

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“…These studies have clearly shown that, under conditions of a few millimolar concentrations of vanadate with equivalent amounts of ligand at neutral pH, the major product of the reaction is a binuclear bisligand product. Early studies proposed that the coordination about the vanadium in this type of product was trigonal bipyramidal (21), although there has been some controversy over the details of the structure (5,16,18). A recent X-ray structure of an adenosine-vanadate dimer showed a slightly distorted square-pyramidal coordination about each of the vanadium nuclei of the dimer in the crystalline material (22).…”

Section: Uridine 56-dihydrouridine and Methyl P-dribofuranoside Plmentioning

confidence: 99%

“…The predominant products are dimeric in nature and their formation constants are large compared to those of the monomeric precursors. Recent work (4,5) has evaluated the formation constant for the 2:2 complex and has also provided a value for the formation constant of the monomeric (1: 1) complex. The nature of this equilibration process was not appreciated at the time of the original inhibition studies.…”

Section: Introductionmentioning

confidence: 99%

Influence of vanadium(V) complexes on the catalytic activity of ribonuclease A. The role of vanadate complexes as transition state analogues to reactions at phosphate

Leon-Lai¹,

Gresser²,

Tracey³

1996

Can. J. Chem.

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Abstract:The interactions of vanadate and its complexes of uridine, 5,6-dihydrouridine, and methyl P-D-ribofuranoside with bovine pancreatic ribonuclease A (RNase A) (EC 3.1.27.5) were studied by 5 1~ NMR spectroscopy and enzyme kinetics. From kinetic studies, it was found that neither inorganic vanadate nor the methyl P-D-ribofuranoside-vanadate complex significantly inhibited the RNase A catalyzed hydrolysis of uridine 2',3'-cyclic monophosphate. The NMR binding studies were in full agreement with the kinetics studies and showed that neither inorganic vanadate nor the methyl P-D-ribofuranoside-vanadate complex was bound tightly by the enzyme. Approximate binding constants were (5.0 + 1.0) x M and (3.0 + 0.6) x M for the uridine-and 5.6-dihydrouridine-vanadate complexes, respectively. An induced-fit mechanism is suggested, in which the pyrimidine subsite of the active site of RNase A must be fully occupied for the enzyme to be able to tightly bind the transition state or transition state analog. Calculation of the binding energies of vanadate complexes in ribonuclease, phosphoglycerate mutase, and phosphoglucomutase revealed an excess of binding energy over the analogous phosphate derivative of about 25 kJ/mol for all enzymes, even though the binding constants themselves varied by about six orders of magnitude. This energy represents about 40% of that expected to be available for a trigonal-bipyramidal transition state and requires a reassessment of the role of vanadate as a transition state analogue for phosphate transfer.Key words: vanadate, ribonuclease, transition state, binding constants, phosphate analogues, kinetics.Resum6 : Faisant appel a la spectrscopie RMN du 5 1~ et de la cinCtique des enzymes, on a CtudiC les interactions entre le vanadate et ses complexes de I'uridine, de la 5,6-dihydrouridine et du P-D-ribofuranoside de mCthyle avec la ribunuclease A du pancrCas de boeuf (RNase A) (EC 3.1.27.5). Sur la base des Ctudes cinCtiques, on a trouvC que, vis-a-vis de I'hydrolyse du monophosphate 2',3'-cyclique de I'uridine de la RNase A, ni le vanadate inorganique ni le complexe du P-D-ribofuranoside de mCthyle-vanadate n'inhibent cette rCaction d'une f a~o n significative. Les Ctudes par RMN ont montrt qu'il ne se produit aucune fixation entre ces matCriaux et elles Ctaient en parfait accord avec les ttudes cinCtiques; elles montrent aussi que ni le vanadate inorganique ni le complexe du P-D-ribofuranoside de mCthyle-vanadate ne se complexent fortement avec I'enzyme. Les constantes apparentes de fixation ont respectivement de (5,O + 1.0) x M et (3,O + 0.6) x M pour les complexes de I'uridine et du 5,6-dihydrouridine avec le vanadate. On propose un mCcanisme induit d'ajustement dans lequel il est important que tout le sous site de la pyrimidine du site actif de la RNase A soit occupC pour que I'enzyme soit capable de bien fixer 1'Ctat de transition ou son analogue. Des calculs d'Cnergie de fixation des complexes du vanadate dans la ribonucltase, la phosphoglycCratemutase ou la phosphoglucomutase ont rCvC...

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Proton and vanadium-51 NMR investigation of the complexes formed between vanadate and nucleosides

Cited by 35 publications

References 0 publications

Stereochemical requirements for the formation of vanadate complexes with peptides

Stereochemical requirements for the formation of vanadate complexes with peptides

Pentavalent Organo-Vanadates as Transition State Analogues for Phosphoryl Transfer Reactions

Influence of vanadium(V) complexes on the catalytic activity of ribonuclease A. The role of vanadate complexes as transition state analogues to reactions at phosphate

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