Open AccessA proton‐nuclear‐magnetic‐resonance study at 500 MHz on Megasphaera elsdenii flavodoxin
Author(s) -
MOONEN Chrit T. W.,
MÜLLER Franz
Publication year - 1984
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1984.tb08103.x
Subject(s) - chemistry , flavin group , amide , proton nmr , proton , redox , flavodoxin , nuclear overhauser effect , hydroquinone , carbon 13 nmr satellite , resonance (particle physics) , spectral line , nuclear magnetic resonance , nuclear magnetic resonance spectroscopy , crystallography , ferredoxin , fluorine 19 nmr , stereochemistry , inorganic chemistry , organic chemistry , physics , particle physics , quantum mechanics , enzyme , astronomy
1 H NMR studies were performed on the three redox states of Megasphaera elsdenii flavodoxin. The results show that the protein is remarkably stable, as concluded from amide proton exchange studies. Some amide protons are still present in the 1 H NMR spectrum even after one month in 2 H 2 O at 33°C (pH 8.3). The reactivity of the exchangeable protons can be grouped into three categories, i.e. t 1/2 > 5min, 10s ≲ t 1/2 ≲ 5 min, and t 1/2 ≪ 10s. The amide proton exchange reactions are hardly dependent on the redox state. Optimal resolution of 1 H NMR spectra is obtained at 33°C, independent of the redox state. No conformational change of the protein is observed in the pH range between 6 and 8.5. Assignments of resonances to protons of flavin and of some amino acid residues are established in both the oxidized and the hydroquinone state using chemically and isotopically substituted flavins and the driven nuclear Overhauser technique. Preliminary two‐dimensional 1 H‐ 1 H correlated spectra show that the protein is amenable to two‐dimensional NMR techniques. Previous assignments are confirmed by this technique.