X-ray crystal structure analysis of -amino acid:Pyruvate aminotransferase and wheat gliadin

1. 假单胞菌sp. F-126 -氨基酸：丙酮酸氨基转移酶的结构[EC 2.6.1.18]。这种酶的三维结构是用光子工厂的同步加速器辐射源在2.0分辨率下测定的。单晶属于正交系，属于I222空间群，单晶尺寸为a=124.7, b=137.9, c=61.5，单晶中含有2个分子。利用新研制的配有富士成像板的Weissenberg相机，以1.8分辨率采集了天然晶体及mersalyl和K_2PtCl_4两种衍生物晶体的三维衍射强度数据。采用多重同构置换法确定反射相位。在低分辨率(6)和高分辨率（2.0）分析下，模型的最终平均价值值<m>分别为0.70和0.57。该酶由4个相同的亚基组成，即呈松散的四聚体排列，由两个紧密结合的单体组成两个相同的二聚体。该酶分子具有4个活性中心，含有446个氨基酸残基，每1个亚基（40 × 45 × 55）含有1个磷酸吡哆醛，分子量约为47500道尔顿。关于二级结构，它在一个亚单元中包含12个螺旋和2个薄片。采用高效液相色谱法分离纯化了3种小麦麦胶蛋白（4A-1、4A-2、4B），并对其化学性质进行了分析。纯化的-麦胶蛋白具有所有型氨基酸组成。从n端氨基酸序列确定其中一个（4A-1）属于_2-麦胶蛋白，另一个（4B）属于_3-麦胶蛋白。从CD谱估计，纯化的_3-麦胶蛋白具有-螺旋结构（26.9%）和-结构（32.1%），这些二级结构被认为定位于蛋白质分子中。用小角x射线散射法和电镜观察对_3-麦胶蛋白的分子形态进行了研究。从x射线小角度散射的结果，证实了它是一个长椭球体。然而，从小角度x射线散射数据证明，_3-麦胶蛋白分子的电子显微图像并不像模型所模拟的那样薄。少

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 … More 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 -gliadinsThree 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