1993 Fiscal Year Final Research Report Summary
Elucidation of structure-function relationships of soybean glycinin by protein engineering
| Project/Area Number |
04660144
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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 |
製造化学・食品
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
UTSUMI Shigeru Kyoto University, Res.Inst.Food Sci., Assoc.Prof., 食糧科学研究所, 助教授 (40111976)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Soybean proteins / Glycinin / Protein engineering / Structure-function relationships / Gelation / Emusification / X-ray crystallography |
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| Research Abstract |
Glycinin is one of the dominant storage proteins of soybean seeds. The relationships between the structure and the food functional properties of glycinin were investigated at the molecular level by means of protein engineering. Glycinin was modified on the basis of its structural characteristics and the relationships between the structure and the functional properties elucidated at the subunit level. The functional properties of the modified proglycinins expressed in E.coli were measured. The results suggest that the hydrophobicity of the C-terminal region is closely related to emulsification, that the disulfide bond 12-45 plays an important role in the initiation of the disulfide exchange reaction required for gelation, that the number and the topology of free sulfhydryl residues are closely related to gelation, and that the factors of the structural instability desired for gelation and emulsification are different each other.
Crystals of the normal and modified proglycinins (DELTAI, DELTAV8, IV+4Met, V+4Met, Gly12, Ser88) expressed in E.coli have been grown. The crystals of normal, DELTAI, V+4Met Gly12 and Ser88 diffracted X-rays sufficiently for crystallographic analysis. Normal, DELTAI, Clyl2 and Ser88 crystals belong to the tetragonal system, space group P4_1 or P4_3 with unit cell dimensions a=b=114.3-115.9 A and c=145.1-147.1 A.V+ 4Met crystals are monoclinic, belonging to space group P2 with unit cell parameters a=118.7 A, b=78.1 A, c=109.9 A and beta=119ﾟ. The number of protomers/asymmetric unit of these crystals is calculated to be around 3. This value is consistent with the fact that proglycinins are trimers. These data indicate that these crystals examined here are suitable for X-ray crystallography to elucidate the relationships between the structure and the functional properties of glycinin at molecular level.
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