1990 Fiscal Year Final Research Report Summary
Structure and Function of Lipophorin in Insect Blood
| Project/Area Number |
01540586
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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 |
動物発生・生理学
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| Research Institution | Hokkaido University |
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Principal Investigator |
KATAGIRI Chihiro Hokkaido Univ. Inst. Low Temp. Sci., Instructor, 低温科学研究所, 助手 (90002245)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Lipoprotein / Lipophorin / Insect blood / Apoprotein / Diacylglycerol / Lipase / Liposome |
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| Research Abstract |
Lipophorin is a widely distributed circulating lipoprotein in insects. Lipophorin acts as a reusable shuttle to transport a variety of lipids between the sites of storage, synthesis and absorption, and the tissues that use lipids as metabolic fuel or as structural components. We have already proposed a three-layer model of lipophorin using a small angle X-ray scattering method ; a quasispherical particle of diameter 168A with an outer shell (24A of phospholipid and apolipophorin I (M_r = 2.5 x 10^5), a middle layer (23A of diacylglycerol and apolipophorin II (M_r = 0.8 x 10^5), and a core (37A of hydrocarbons. However, little is known about the mechanism of lipid transport by lipophorin. A detailed knowledge of the roles of each apolipophorin is necessary for a basic understanding how lipophorin loads and unloads lipid, and how lipophorin regulates lipid metabolism. In the present study, we succeeded in isolating each apolipophorin which is now tried to be incorporated into liposome. These reconstituted lipophorin contributes to further studies for understanding the roles of each apolipophorin in lipid transport. We also succeeded in removing diacylglycerol from a lipophorin particle without destroying lipophorin itself. For this purpose, fungal lipase was useful to hydrolyze diacylglycerol in lipophorin. This will help to understand how lipid is unloaded. These efforts will open a new field on lipoprotein metabolism. Furthermore, we found a hydrocarbon-rich diacylglycerol-poor lipophorin in the blood of a Colorado potato beetle. Such a diacylglycerol-poor lipophorin has never been reported before. After purification, we examined its physiological functions and proposed its structural model.
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