Hydrogen-deuterium exchange kinetics of the C-2 protons of imidazole and histidine compounds

Jh, Bradbury; Be, Chapman; Fa, Pellegrino

doi:10.1021/ja00799a063

Cited by 56 publications

(38 citation statements)

References 2 publications

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“…Bradbury et al (20) found that the second-order rate constant for C(2)-H deuterium exchange of imidazole acetic acid was 6.412.9, i.e., 2.2 times smaller than that for imidazole. The results of the above two studies suggest that the increase in rate due to the ammonium group is equal to the rate-retarding effect of the carboxylate, which is consistent with the k for histidine and irnidazole, and for 1 -methylhistidine and 1 -methylimidazole, to be of the same order of magnitude.…”

Section: Coo-mentioning

confidence: 99%

“…The second-order rate constants k and k' derived from the kinetic analysis can be compared with the corresponding rate constants previously reported for histidine ( 19,20), imidazole (3, 2 1 ) , and benzimidazole (2 1) and their 1 -methyl derivatives (3, 17), Table 2. There are several interesting points that arise from the data presented in Table 2.…”

Section: Reactiviry Relationshipsmentioning

confidence: 99%

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Metal ion – biomolecule interactions. Part 14. Methylmercury and hydrogen ion catalysis of C(2)-H isotopic exchange in 1-methylhistidine

Buncel¹,

Joly²,

Yee³

1989

Can. J. Chem.

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. Can. J . Chem. 67, 1426Chem. 67, (1989. The rate constants for detritiation from the C(2) position of 1-meth~l[2-~~]histidine have been determined in a series of aqueous buffers at 8S0C. The resulting sigmoidal rate-pH profile was indicative of a mechanism involving hydroxide ion attack on the N(3)-protonated (4) and the amino-protonated (5) forms of 1-methylhistidine, and dissection of the kinetic data allowed the extraction of the second-order rate constants for the two pathways, k and k t . The unusually large value of k' for a species not protonated at N(3) of the imidazole ring suggested the involvement of a kinetically equivalent zwitterionic form of the substrate (7). Comparison of the rate constant k with values determined previously for closely related substrates, such as histidine, 1-methylimidazole, and imidazole, led to the use of FMO theory to explain the effect of the various structural changes, e.g., the effect of methylation and a positively charged side chain on k and k'. The addition of MeHgN03 resulted in a decrease in the pseudo-first-order rate constant for dehitiation. The rate retardation was discussed in terms of two mechanisms (Schemes 2 and 3). Analysis of the data in terms of the various metal-ion-coordinated species present under the experimental conditions showed that the reactivity of the protonated substrate greatly exceeds that of the metal-coordinated species. The difference in the catalytic ability of H+ vs. MeHg+ is discussed in terms of the extent of positive charge developed on the ligating heteroatom in the ylide (carbenoid) reaction intermediate.Key words: methylmercury, 1-methylhistidine, isotopic exchange, proton transfer, metal ion catalysis.ERWIN BUNCEL, HELEN A. JOLY et DIANE C. YEE. Can. J. Chem. 67, 1426Chem. 67, (1989.On a dktermink les constantes de vitesse de la dktritiation h partir de la position C(2) de la rn~th~l-l[~~-2]-histidine dans une skrie de solutions tampons ?i 85°C. Le profil sigmoidal de la courbe de vitesse en fonction du pH obtenue, tkmoigne I'existence d'un mkcanisme faisant intervenir l'attaque de l'ion hydroxyle sur les formes protonkes en N(3) (4) et amino-protonke (5) L'addition du MeHgN03 conduit h une diminution de la constante de vitesse de pseudo ordre un de la dktritiation. On discute de la diminution de la vitesse en fonction de deux mkcanismes (schkmas 2 et 3). L'analyse des donnkes en fonction des diverses espi?ces ion mktallique-coordonnk prksentes dans les conditions exp6rimentales dkcrites, montre que la rkactivitk du substrat proton6 exckde de beaucoup celle des espkces mktalliques coordonnkes. On discute de la diffkrence de pouvoir catalytique de H+ versus MeHg+ en fonction du taux de charge positive dkveloppke au niveau de l'hktkroatome jouant le r6le de ligand dans l'intermkdiaire (carbknoide) de rkaction de l'ylide.Mots clks : mercure-mkthyle, mtthyl-1-histidine, tchange isotopique, transfert de proton, catalyse d'ion mttallique.[Traduit par la revue]Histidine (1) is one of the most important amino acids found in biologi...

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Section: Coo-mentioning

confidence: 99%

Section: Reactiviry Relationshipsmentioning

confidence: 99%

Metal ion – biomolecule interactions. Part 14. Methylmercury and hydrogen ion catalysis of C(2)-H isotopic exchange in 1-methylhistidine

Buncel¹,

Joly²,

Yee³

1989

Can. J. Chem.

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“…The pK is equal to the pH at which log (6, -S)/(S -6,) = 0 [34]. [35,36] Bovine a-lactalbumin was dissolved in 2H20 and allowed to stand at room temperature at pH % 6 for about 30 min to replace readily exchangeable protons with 2H. The solution was lyophilised.…”

Section: Pmr Spectroscopy and Histidine Titrutionsmentioning

confidence: 99%

“…In two separate experiments in unbuffered solutions the pH increased by 0.20 over 5 days and by 0.28 in 6 days. When the pH was readjusted to pH 6.8 albumin undergoes a slow, irreversible conformational change at pH 8.5, which prevents one obtaining the rate constants for exchange as a function of pH [36].…”

Section: Histidine H -2h Exchangementioning

confidence: 99%

Proton-Magnetic-Resonance Spectroscopic Study of the Histidine Residues of Bovine alpha-Lactalbumin

Bradbury

Norton

1975

Eur J Biochem

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A study of the three histidine residues of bovine α‐lactalbumin has been made using proton magnetic resonance (PMR) spectroscopy in order to obtain information of their environments in the protein and thereby to test in part the previously proposed structure. PMR titration curves are obtained for the H‐4 resonances using difference spectroscopy and for the H‐2 resonances and the 1H–2H exchange rates of the H‐2 protons have been measured. The assignment of resonances to particular histidine residues is achieved by utilising their selective reaction with iodoacetate in conjunction with a PMR study of the carboxymethylation of α‐N‐acetyl‐l‐histidine. The H‐2 and H‐4 resonances labelled 1, 2and 3 starting from the downfield end of the spectrum are assigned to histidine residues 107, 68 and 32 respectively. Their apparent pK values at low ionic strength and 20°C are 5.78, 6.49 and 6.51 respectively. The experimental results on two histidine residues are consistent with the predictions of the proposed structure, which indicate that histidine‐68 is an external residue and histidine‐32 is partially buried and in the vicinity of aromatic residues. The experimental data on histidine 107 can also be rationalised with less certainty in terms of the proposed structure, which indicates a partially buried residue that may be involved in hydrogen bonding.

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“…However, the pseudo first-order rate constant of deuterium exchange for C-2H is 1.8 x 10e6 s-l at pH 8.5 and 30°C when cro retains its native conformation [ 10,111. This indicates that His-35 is accessible to the solvent [12] and does not interact with other ionizable groups in the protein. It is very likely that, just as in the crystal [2], His-35 in solution is located on the surface of a protein globule.…”

Section: Resultsmentioning

confidence: 99%

Studies of the structure of bacteriophage λ cro protein in solution

Kurochkin¹,

Кирпичников²

1982

FEBS Letters

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Hydrogen-deuterium exchange kinetics of the C-2 protons of imidazole and histidine compounds

Cited by 56 publications

References 2 publications

Metal ion – biomolecule interactions. Part 14. Methylmercury and hydrogen ion catalysis of C(2)-H isotopic exchange in 1-methylhistidine

Metal ion – biomolecule interactions. Part 14. Methylmercury and hydrogen ion catalysis of C(2)-H isotopic exchange in 1-methylhistidine

Proton-Magnetic-Resonance Spectroscopic Study of the Histidine Residues of Bovine alpha-Lactalbumin

Studies of the structure of bacteriophage λ cro protein in solution

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