| Project/Area Number |
60480134
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
General medical chemistry
|
|---|
| Research Institution | Kanazawa University |
|---|
Principal Investigator |
YONEYAMA Yoshimasa Professor, Kanazawa University School of Medicine., 医学部, 教授 (10019515)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
MAWATARI Kazuhiro Lecturer, Kanazawa University School of Allied Medical Professions., 医療技術短期大学部, 講師 (50135050)
MATSUKAWA Shigeru Lecturer, Kanazawa University School of Medicine., 医学部, 講師 (00092809)
|
|---|
| Project Period (FY) |
1985 – 1986
|
| Project Status |
Completed (Fiscal Year 1986)
|
| Budget Amount *help |
¥6,100,000 (Direct Cost: ¥6,100,000)
Fiscal Year 1986: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1985: ¥3,400,000 (Direct Cost: ¥3,400,000)
|
|---|
| Keywords | Hemoglobin / Oxygen affinity / Cooperativity / Resonance Raman / Iron-Histidine bond / 蛍光ラベル / エフェクター |
|---|
| Research Abstract |
The outline of the stereochemical mechanism of the cooperative oxygen binding of hemoglobin (Hb) has been well documented. However, the modulation mechanism of oxygen affinity and the trigger mechanism for the R-T structural transition remain unproven experimentally. To resolve these problems we have been investigated the structural and functional relationships of abnormal Hbs with an amino acid substitution at the <(alpha)_1(beta)_2> contact. The aim of this study is to point out the structural element(s) essential for allosteric oxygen binding by comparing the structural alterations with functional ones of various abnormal Hbs.
Analysis of Oxygen equilibrium curves for normal and abnormal Hbs in terms of the two-state allosteric model suggested that the abnormal allosteric oxygen binding of Hb is due to altered molecular properties of the deoxy-T state. To clarify the molecular basis of this situation, the resonance Raman spectra in the low-frequency region of deoxy Hbs and the binding of fluorescence-labelled allosteric effector (MANT-ATP) to deoxy Hbs were examined.
The high-affinity deoxy Hb gave the Fe-His stretching Raman line at 220-220 <cm^(-1)> similar to that of the isolated chains, while the low-affinity one gave the Raman line at 214-216 <cm^(-1)> . However, deoxy Hbs with intermediate levels of oxygen affinity unexpectedly exhibited the Raman line at intermediate frequencies. Furthermore, this varied frequencies of Fe-His stretching Raman lines for various Hbs was found to correlate well with varied oxygen affinities of deoxy-T state. In contrast, the MANT-ATP binding experiments showed that the stucture of the organic phosphate binding site of abnormal Hbs is almost identical to that of Hb A.
Based on the above results, we concluded that the Fe-His bond presumably comprises an important part of the regulation mechanism for hemoglobin oxygen affinity and quaternary structural changes.
|
