1992 Fiscal Year Final Research Report Summary
Structural and Functional Analysis of Hemoproteins Under High Pressure by Las Photolysis Measurements
| Project/Area Number |
03453009
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
物理化学一般
|
|---|
| Research Institution | KYOTO UNIVERSITY |
|---|
Principal Investigator |
MORISHIMA Isao Kyoto Univ., Engineering, Professor, 工学部, 教授 (50026093)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
ISHIMORI Koichiro Kyoto Univ., Engineering, Instructor, 工学部, 助手 (20192487)
WATANABE Yoshihito Kyoto Univ., Engineering, Associate Professor, 工学部, 助教授 (10201245)
|
|---|
| Project Period (FY) |
1991 – 1992
|
| Keywords | Myoglobin / Hemoglobin / High-Pressure Kinetics / Laser Photolysis / Activation Volume / Ligand Binding / Electron Transfer / CO Rebinding |
|---|
| Research Abstract |
1. Several site-specific mutants of human myoglobin(Mb) have been prepared in order to examine the influence of highly conserved leucine residues located in the hydrophobic clusters in the heme distal and proximal site on the heme environmental structures and ligand binding properties. Structural and ligand binding characterization of these recombinant proteins were studied by NMR, IR and laser photolysis measurements under different pressures. The leucine 29 mutants exhibited unusual pressure dependence of CO binding rate constant and the resulting pressure dependence of the activation volume implies that pressurization affects the fractional distributions of multi-conformers of Mb so that the fast CO rebinding conformers is increased under pressure.
2. The effects of pressure on the recombination kinetics of CO binding to the isolated alpha and beta chains of human hemoglobin(Hb) were studied. Pressure dependent activation volume change from negative to positive values in the bimolecular CO association reaction was observed for both isolated chains. This finding was attributed to a change in the rate-determining step from the bond formation to the ligand migration process.
3. We have also studied pressure effects on the CO association reaction for cytochrome P-450. It was found that the activation volume is quite sensitive to the presence or absence of the substrate, the molecular structure of the substrate.
4. Finally, we have made a preliminary study on the pressure effect on the intraprotein electron transfer reaction rate.
|
