Jurnak F, McPherson A, Wang A H, Rich A
J Biol Chem. 1980 Jul 25;255(14):6751-7.
The tetragonal crystalline form of the trypsin-treated Escherichia coli protein elongation factor Tu has been analyzed by biochemical and x-ray crystallographic techniques. The crystals contain two tightly associated polypeptide fragments of molecular weight 36,000 and 6,500 which represent 97% of the native enzyme. The crystals do not contain a short internal polypeptide fragment of 14 amino acids which dissociates from the native enzyme following mild trypsin digestion. The short fragment has been implicated in the aminoacyl-tRNA binding function and its location has been determined. The structure of the modified enzyme in the P4(3)2(1)2 crystal form has been determined to 5 A resolution by x-ray diffraction methods. The protein consists of two domains: the larger domain exhibits considerable alpha helical characteristics and the smaller domain has no identifiable secondary structural features. The relationship between the double domain structure of the enzyme and its biochemical properties is discussed.
用生物化学和X射线晶体学技术分析了经胰蛋白酶处理的大肠杆菌蛋白质延伸因子Tu的四方晶体形式。晶体包含两个紧密结合的多肽片段，分子量分别为36,000和6,500，占天然酶的97%。晶体中不包含一个14个氨基酸的短内部多肽片段，该片段在温和的胰蛋白酶消化后会从天然酶上解离。该短片段与氨酰-tRNA结合功能有关，其位置已确定。通过X射线衍射方法，已将P4(3)2(1)2晶体形式的修饰酶结构解析到5埃分辨率。该蛋白质由两个结构域组成：较大的结构域具有相当多的α螺旋特征，较小的结构域没有可识别的二级结构特征。讨论了该酶的双结构域结构与其生化性质之间的关系。
