1995 Fiscal Year Final Research Report Summary
Expression of latent functions of heme proteins triggered by synthetic bilayr membranes
| Project/Area Number |
06453216
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Bioorganic chemistry
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
KUNITAKE Toyoki Faculty of Engineering, Kyushu University Professor, 工学部, 教授 (40037734)
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| Co-Investigator(Kenkyū-buntansha) |
ANDO Reiko Faculty of Engineering, Kyushu University Research Assistant, 工学部, 教務員
KIMIZUKA Nobuo Faculty of Engineering, Kyushu University Associate Professor, 工学部, 助教授 (90186304)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Cytochrome-c / Unfolding / Maleic acid / Peroxydase / Tertiary structure / Heme-protein / Protein engineering |
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| Research Abstract |
The expression of unique functions of heme proteins is determined by the heme-apoprotein interaction. A new methodology of the functional control become feasible if this interaction is modified via the tertiary structure of proteins. The lysine residues present on the surface of cytochrome c (Cyt-c) play an important role in the maintenance of the tertiary structure. When most of the its amino group is maleylated, the globular structure of Cyt-c is converted to a partially unfolded structure. Interestedly, the new structure returns to the original globular form by increasing the salt concentration of the medium. This conversion is accompanied by the gradual change of the axial coordination of the heme from HO-Fe-His18 to Met80-Fe-His18. In the functional aspect, although the natural Cyt-c acts as electron transfer protein, the maleylated protein shows a peroxydase like activity in the partially unfolded structure. Upon reconversion of the protein structure by addition of salts in the medium, the peroxydase activity is suppressed and electron transfer function is strengthened. Thus, the modification of the surface lysine residue leads to the concomitant changes of the tertiary structure and the enzyme function. This methodology is also applicable to myoglobin, showing its rich possibility in enzyme engineering. It reveals a new aspect that is quite different from the conventional enzyme modification by the altered primary structure, and may be related to the concept of catalytic molten globules that are apparently involved in the process of molecular evolution.
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