Structural and dynamic properties of the heme pocket in myoglobin probed by optical spectroscopy

• Published in: Biopolymers
• Main Authors: Cupane, Antonio, Leone, Maurizio, Vitrano, Eugenio, Cordone, Lorenzo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1988
• Subjects: Sperm whale
• Online Access: http://dx.doi.org/10.1002/bip.360271209; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fbip.360271209; https://onlinelibrary.wiley.com/doi/pdf/10.1002/bip.360271209

Abstract We report the optical absorption spectra of sperm whale deoxy‐, oxy‐, and carbonmonoxymyoglobin in the temperature range 300–20 K and in 65% glycerol or ethylene glycol–water mixtures. By lowering the temperature, all bands exhibit half‐width narrowing and peak frequency shift; moreover, the near‐ir bands of deoxymyoglobin show a marked increase of the integrated intensities. Opposed to what has already been reported for human hemoglobin, the temperature dependence of the first moment of the investigated bands does not follow the behavior predicted by the harmonic Franck–Condon approximation and is sizably affected by the solvent composition; this solvent effect is larger in liganded than in nonliganded myoglobin. However, for all the observed bands the behavior of the second moment can be quite well rationalized in terms of the harmonic Franck–Condon approximation and is not dependent on solvent composition. On the basis of these data we put forward some suggestions concerning the structural and dynamic properties of the heme pocket in myoglobin and their dependence upon solvent composition. We also discuss the different behaviors of myoglobin and hemoglobin in terms of the different heme pocket structures and deformabilities of the two proteins.