1992 Fiscal Year Final Research Report Summary
Studies of Protein Folding with Gene Manipulation and X-ray Solution Scattering -The Case of Staphylococcal Nuclease-
| Project/Area Number |
02680217
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
生物物性学
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| Research Institution | Osaka University (1992)
Tohoku University (1990-1991) |
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Principal Investigator |
KATAOKA Mikio Osaka University, Faculty of Science, Associate Professor, 理学部, 助教授 (30150254)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Protein Folding / Gene Manipulation / X-ray Solution Scattering / Staphylococcal Nuclease / Molten Golbule / Non-native Structure |
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| Research Abstract |
The structural information of unfolded state is essential for the better understanding of protein folding. We have revealed that X-ray solution scattering is useful and unique method to derive the compactness and the globularity of a protein molecule, which are estimated from the radius of gyration and the integral intensity of Kratky plot. The compactness and the globularity are the important factors to describe the extent of folding.
Urea denaturation of Staphylococcal nuclease has been studied by X-ray solution scattering. The denaturation curve obtained from the compactness shows a good agreement with those obtained from CD and fluorescence in the case of wild type nuclease, while the denaturation curve of the mutant belonging to the class m- is different between X-ray and CD or fluorescence. This result strongly suggests that the acquisition of the compactness occurs earlier stage than the formation of the secondary structure.
Staphylococcal nuclease fragment which lacks 13 amino acid residues from its C-terminus is unfolded under a physiological condition, while it is folded upon the addition of the inhibitor, pdTp. The fragment is a good model system for the folding study. The mutant fragments which have amino acid substitutions belonging to class m- are more compact than wild type fragment, while the mutant fragments with amino acid substitution of class m+ are much larger than wild type. The m- fragment takes a different inner structure from native protein. The m+ fragment takes a chain-like conformation. These results indicate that the effect of amino acid substitution is appeared in the unfolded state as well as the folded state.
X-ray solution scattering is successfully applied to the studies of various conformational states of the other proteins.
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