Structural dynamics of distal histidine replaced mutants of myoglobin accompanied with the photodissociation reaction of the ligand.
Protein dynamics observed by the transient grating (TG) method are studied for some site-directed mutants at the distal histidine of myoglobin (H64L, H64Q, H64V). The time profiles of the TG signals are very sensitive to the amino acid residue of the 64 position. It was found that the sensitivity is mostly caused by the different rates of the ligand escape from the protein to solvent and the magnitude of the molecular volume change. Several molecular origins of the volume difference between MbCO and Mb, such as the electrostatic interaction in the distal pocket, movement of helices, and distal water, are proposed. Interestingly, the volume difference between the CO-trapped Mb inside the protein interior and Mb is similar to that of the partial molar volume of CO in organic solvent. The effect of mutation on the nature of the CO trapped site is discussed.
Sakakura
Masaaki
M
Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
Morishima
Isao
I
Terazima
Masahide
M
D019943:Amino Acid Substitution; D000818:Animals; D006639:Histidine; D008024:Ligands; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009211:Myoglobin / Q000737:chemistry* / Q000528:radiation effects; D010782:Photolysis; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D012680:Sensitivity and Specificity; D013816:Thermodynamics; D014907:Whales
D008024:Ligands; D009211:Myoglobin; D011994:Recombinant Proteins; C018013:carboxymyoglobin; D006639:Histidine