1988 Fiscal Year Final Research Report Summary
X-ray crystal structure analysis of -amino acid:Pyruvate aminotransferase and wheat gliadin
| Project/Area Number |
62560085
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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 |
応用生物化学・栄養化学
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| Research Institution | Kyoto University |
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Principal Investigator |
AIBARA Shigeo The Research Institute for Food Science Associate Professor, 食糧科学研究所, 助教授 (20027197)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Wheat / Gliadin / Transaminase / Crystal structure / Small angle X-ray scattering / シンクロトロン放射光 |
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| Research Abstract |
1. Structure of -amino acid : pyruvate aminotransferase from Psedomonas sp. F-126 [EC 2.6.1.18.]
The three dimensinal structure of this enzyme was determined at 2.0 resolution using the synchrotron radiation source at the Photon Factory, Tsukuda. The single crystals belong to the orthorhombic system and the space group of I222 with a unit cell dimensions, a=124.7 , b=137.9 , and c=61.5 , and contain 2 molecules in a unit cell. Three dimensional diffraction intensity data were collected from native crystals and crystals of two derivatives, mersalyl and K_2PtCl_4 at 1.8 resolution with a newly deveroped Weissenberg camera equipped with Fuji Imaging Plate as a detector. Phases of the reflections were determined by the multiple isomorphous replacement method. A final mean figure-of-merit, <m>, is 0.70 and 0.57 for the models at the low resolution (6 ) high resolution (2.0 )analyses, respectively. This enzyme consists of 4 identical subunits, that is, shows a tetrameric arrangement of loosel
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y binding two identical dimers which are made up by tightly binding two monomers. The enzyme molecule possesses 4 active centers and has 446 amino acid residues and 1 pyridoxal phosphate per 1 subunit (40 x 45 x 55 ) with molecular weight of about 47,500 daltons. Regarding the secondary structure, it contains 12 helixes and 2 -sheets in a subunit.
2. Molecular shape of wheat -gliadins
Three kinds of wheat gliadins (4A-1, 4A-2, 4B) were separated and purified by HPLC, and the chemical characteristics of these proteins are elucidated. The purified -gliadins have all the -type amino acid composition. It is ascertained from the N-terminal amino acid sequences that one of them (4A-1) is classified into _2-gliadin and another one (4B) is _3-gliadin. The purified _3-gliadin possesses -helixes (26.9%) and -structures (32.1%) from the estimation of CD spectrum, and these secondary structures assumed to be localized in the protein molecule. The molecular shape of the _3-gliadin is investigated with both of small angle X-ray scattering method and the observation of electron micrography. From the results of small angle X-ray scattering, it was confirmed to be a prolate ellipsoid. However, the electron micrographic images of the _3-gliadin molecule were proved to be not so thin as to the model simulated from the small angle X-ray scattering data. Less
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