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

1. - 氨基酸的结构：来自假单胞菌属F-126的丙酮酸氨基转移酶[EC 2.6.1.18.]该酶的三维结构是在2.0分辨率下使用光子工厂（Tsukuda）的同步辐射源测定的。单晶属于正交晶系，空间群为I222，晶胞尺寸为a=124.7，B=137.9，c=61.5，并且在晶胞中包含2个分子。本文用新研制的Weissenberg照相机和Fuji成像板作探测器，在1.8分辨率下，对天然晶体和两种衍生物（汞撒利和K_2PtCl_4）的晶体进行了三维衍射强度数据的采集。反射的相位由多重同晶置换法确定。在<m>低分辨率（6）和高分辨率（2.0）分析下，模型的最终平均优值分别为0.70和0.57。该酶由4个相同的亚基组成，即显示松散的四聚体排列。 ...更多信息 y结合两个相同的二聚体，所述二聚体由两个单体紧密结合而成。该酶分子具有4个活性中心，每1个亚基（40 × 45 × 55）具有446个氨基酸残基和1个磷酸吡哆醛，分子量约为47，500道尔顿。在二级结构中，每个亚基含有12个螺旋和2个折叠.小麦醇溶蛋白的分子形态用高效液相色谱法分离纯化了3种小麦醇溶蛋白（4A-1、4A-2、4 B），并对其化学性质进行了鉴定。纯化的醇溶蛋白具有全部的α-型氨基酸组成. N-末端氨基酸序列分析表明，其中一个（4A-1）属于_2-醇溶蛋白，另一个（4 B）属于_3-醇溶蛋白。经圆二色谱分析，醇溶蛋白中有26.9%的β-螺旋和32.1%的β-结构，推测这些二级结构位于蛋白质分子中。用X射线小角散射法和电子显微镜观察研究了_3-醇溶蛋白的分子形态。小角X射线散射结果证实它是一个长椭球体。然而，_3-醇溶蛋白分子的电子显微图像被证明不是那么薄，从小角X射线散射数据模拟的模型。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