Conformation of Cobrotoxin in Aqueous Solution as Studied by Nuclear Magnetic Resonance
- 1 December 1979
- journal article
- research article
- Published by Wiley in European Journal of Biochemistry
- Vol. 102 (2), 417-430
- https://doi.org/10.1111/j.1432-1033.1979.tb04257.x
Abstract
The 270-MHz proton NMR spectra of cobrotoxin from Naja naja atra were observed in 2H2O solution. The pKa value (5.93) of His-32 is slightly lower than the pKa value (6.65) of the reference model of N-acetylhistidine methylamide, because of the electrostatic interaction with Arg-33 and Asp-31. The pKa value (5.3-5.4) of His-4 is appreciably low, because of the interaction with the positively charged guanidino group possibly of Arg-59. The hydrogen-deuterium exchange rates in 2H2O solution were measured of cobrotoxin and imidazole-bearing models. The 2nd-order rate constants of N-acetylhistidine methylamide, N-acetylhistidine and imidazole acetic acid satisfy the Bronsted relation. With reference to this Bronsted relation, the imidazole ring of His-32 is confirmed to be exposed. The imidazole ring of His-4 is also exposed and the exchange rate is excessively promoted by the presence possibly of Arg-59 in the proximity. All the methyl proton resonances are assigned to amino-acid types, by conventional double-resonance method and more effectively by the spin-echo double-resonance method. Eight methyl proton resonances are identified as due to the .gamma. and/or .delta.-methyl groups of Val-46, Leu-1, Ile-50 and Ile-52 residues. The proximity of aromatic ring protons and methyl protons is elucidated by the analyses of nuclear Overhauser effect enhancements. The aromatic proton resonances of Trp-29 are affected by the ionizable groups of Asp-31, His-32 and Tyr-35. The methyl groups of Ile-50 are in the proximity to the aromatic ring of Trp-29 and the methyl groups of Ile-52 are in the proximity to Tyr-25. The highest-field methyl proton resonance is due to a Thr residue in the proximity to His-4. The appreciable temperature-dependent chemical shift of this methyl proton resonance suggests a temperature-dependent local conformational equilibrium around the His-4 residue of the first loop of the cobrotoxin molecule.This publication has 27 references indexed in Scilit:
- NMR STUDY ON THE PROTONATION OF IMIDAZOLE RING OF N-ACETYL-l-HISTIDINE METHYLAMIDE, A MODEL FOR HISTIDINE RESIDUES EXPOSED TO AQUEOUS SOLVENTChemistry Letters, 1978
- NMR spectroscopy of large peptides and small proteinsJournal of Magnetic Resonance (1969), 1978
- NOE difference spectroscopy: A novel method for observing individual multiplets in proton NMR spectra of biological macromoleculesJournal of Magnetic Resonance (1969), 1978
- 1H n.m.r. studies of a neurotoxin and a cardiotoxin from Naja mossambica mossambica: Amide proton resonancesBiochemical and Biophysical Research Communications, 1977
- Proton‐Nuclear‐Magnetic‐Resonance Study of the Conformation of Neurotoxin II from Middle‐Asian Cobra (Naja naja oxiana) VenomEuropean Journal of Biochemistry, 1976
- Nuclear magnetic resonance determination of intramolecular distances in bovine pancreatic trypsin inhibitor using nitrotyrosine chelation of lanthanidesBiochemistry, 1976
- Assignment of the histidine proton magnetic resonance peaks of soybean trypsin inhibitor (Kunitz) by a differential exchange techniqueBiochemistry, 1975
- Spin echo double resonance: a novel method for detecting decoupling in Fourier transform nuclear magnetic resonanceJournal of the Chemical Society, Chemical Communications, 1975
- Resolution enhancement of protein PMR spectra using the difference between a broadened and a normal spectrumJournal of Magnetic Resonance (1969), 1973
- A Model Of The Three‐Dimensional Structure Of Snake Venom Neurotoxins Based On Chemical EvidenceInternational Journal of Peptide and Protein Research, 1973