TY - JOUR
T1 - Ligand migration human myoglobin
T2 - Steric effects of isoleucine 107(G8) on O2 and CO binding
AU - Ishikawa, H.
AU - Uchida, T.
AU - Takahashi, S.
AU - Ishimori, K.
AU - Morishima, I.
N1 - Funding Information:
This work was supported by Grant-in-Aid for Science Research on Priority Areas, Molecular Biometallics, from the Ministry of Education, Science, Sports and Culture (08249102) to I.M. H.I. and T.U. were supported by the fellowship of Japan Society for Promotion of Science to Japanese young scientists.
PY - 2001
Y1 - 2001
N2 - To investigate the ligand pathway in myoglobin, some mutant myoglobins, in which one of the amino acid residues constituting a putative ligand-docking site, Ile107, is replaced by Ala, Val, Leu, or Phe, were prepared and their structural and ligand binding properties were characterized. The kinetic barrier for the ligand entry to protein inside was lowered by decreasing the side-chain volume at position 107, indicating that the bulky side chain interferes with the formation of the activation state for the ligand migration and the free space near position 107 would be filled with the ligand in the activation state. Another prominent effect of the reduced side-chain volume at position 107 is to stabilize the ligand-binding intermediate state. Because the stabilization can be ascribed to decrease of the positive enthalpy, the enlarged free space near position 107 would relieve unfavorable steric interactions between the ligand and nearby amino acid residues. The side-chain volume at position 107, therefore, is crucial for the kinetic barrier for the ligand migration and free energy of the ligand-binding intermediate state, which allows us to propose that some photodissociated O2 moves toward position 107 to be trapped and then expelled to the solvent.
AB - To investigate the ligand pathway in myoglobin, some mutant myoglobins, in which one of the amino acid residues constituting a putative ligand-docking site, Ile107, is replaced by Ala, Val, Leu, or Phe, were prepared and their structural and ligand binding properties were characterized. The kinetic barrier for the ligand entry to protein inside was lowered by decreasing the side-chain volume at position 107, indicating that the bulky side chain interferes with the formation of the activation state for the ligand migration and the free space near position 107 would be filled with the ligand in the activation state. Another prominent effect of the reduced side-chain volume at position 107 is to stabilize the ligand-binding intermediate state. Because the stabilization can be ascribed to decrease of the positive enthalpy, the enlarged free space near position 107 would relieve unfavorable steric interactions between the ligand and nearby amino acid residues. The side-chain volume at position 107, therefore, is crucial for the kinetic barrier for the ligand migration and free energy of the ligand-binding intermediate state, which allows us to propose that some photodissociated O2 moves toward position 107 to be trapped and then expelled to the solvent.
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U2 - 10.1016/S0006-3495(01)76123-1
DO - 10.1016/S0006-3495(01)76123-1
M3 - Article
C2 - 11222311
AN - SCOPUS:0035119236
VL - 80
SP - 1507
EP - 1517
JO - Biophysical Journal
JF - Biophysical Journal
SN - 0006-3495
IS - 3
ER -