Ohtsuki T, Takemoto C, Kawai G, Ueda T, Kita K, Kojima S, Kaziro Y, Nyborg J, Watanabe K
Department of Chemistry, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
J Biol Chem. 2001 Jun 15;276(24):21571-7. doi: 10.1074/jbc.M011118200. Epub 2001 Mar 21.
We have found the gene for a translation elongation factor Tu (EF-Tu) homologue in the genome of the nematode Caenorhabditis elegans. Because the corresponding protein was detected immunologically in a nematode mitochondrial (mt) extract, it could be regarded as a nematode mt EF-Tu. The protein possesses an extension of about 57 amino acids (we call this domain 3') at the C terminus, which is not found in any other known EF-Tu. Because most nematode mt tRNAs lack a T stem, domain 3' may be related to this feature. The nematode EF-Tu bound to nematode T stem-lacking tRNA, but bacterial EF-Tu was unable to do so. A series of domain exchange experiments strongly suggested that domains 3 and 3' are essential for binding to T stem-lacking tRNAs. This finding may constitute a novel example of the co-evolution of a structurally simplified RNA and the cognate RNA-binding protein, the latter having apparently acquired an additional domain to compensate for the lack of a binding site(s) on the RNA.
我们在秀丽隐杆线虫的基因组中发现了一种翻译延伸因子Tu（EF-Tu）同源物的基因。由于在一种线虫线粒体（mt）提取物中通过免疫检测到了相应的蛋白质，它可被视为一种线虫mt EF-Tu。该蛋白质在C末端拥有约57个氨基酸的延伸部分（我们将此结构域称为3'），这在任何其他已知的EF-Tu中都未发现。由于大多数线虫mt tRNA缺乏T茎，3'结构域可能与此特征相关。线虫EF-Tu能与缺乏T茎的线虫tRNA结合，但细菌EF-Tu则无法做到。一系列结构域交换实验有力地表明，3结构域和3'结构域对于与缺乏T茎的tRNA结合至关重要。这一发现可能构成了结构简化的RNA与同源RNA结合蛋白共同进化的一个新例子，后者显然获得了一个额外的结构域以弥补RNA上结合位点的缺失。
