Open AccessSolvent‐induced Structural Distortions of Horse Metmyoglobin
Author(s) -
Glandières JeanMarie,
Calmettes Patrick,
Martel Peter,
Zentz Christian,
Massat Alain,
Ramstein Jean,
Alpert Bernard
Publication year - 1995
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1995.tb20381.x
Subject(s) - chemistry , myoglobin , metmyoglobin , heme , formamide , circular dichroism , solvent , hydrogen bond , hydrogen–deuterium exchange , crystallography , molecule , fourier transform infrared spectroscopy , photochemistry , kinetics , hydrogen , organic chemistry , enzyme , physics , quantum mechanics
Structural and dynamic constraints produced by the surrounding solvent on the aquometmyoglobin molecule were investigated by means of circular dichroism and Fourier‐transform infrared spectroscopies, tritium/hydrogen exchange kinetics and small‐angle neutron‐scattering experiments. Formamide and ethanol were chosen as cosolvents because they are known to increase and decrease protein activity, respectively. The CD measurements in the Soret region show that no changes occur in the heme molecular structure nor in the protein near the heme. The results of proton‐exchange kinetics experiments indicate that the conformational dynamics of aquometmyoglobin is only marginally affected by the cosolvents. However, the small‐angle neutron‐scattering spectra strongly suggest that these cosolvents induce some distortions of the tertiary conformation. According to the ultraviolet CD and Fourier‐transform infrared data, the alteration of the tertiary conformation results from changes in both the number of intrachain hydrogen bonds and the structures of β turns of type I' for formamide and of type II for either of the two cosolvents. The use of several techniques allows the present approach to demonstrates that the myoglobin structure is extremely sensitive to its environmental conditions.