Imanaka T, Lee S, Takagi M, Fujiwara S
Department of Biotechnology, Faculty of Engineering, Osaka University, Japan.
Gene. 1995 Oct 16;164(1):153-6. doi: 10.1016/0378-1119(95)00491-n.
The aspartyl-tRNA synthetase (AspRS)-encoding gene from the archaeon, Pyrococcus sp. KOD1 (KOD1), was cloned and sequenced, and expressed in Escherichia coli. The purified AspRS possessed an aminoacyation activity for tRNA extracted from KOD1. Analysis of the deduced amino-acid sequence (438 aa, 50,893 Da) revealed that the AspRS of KOD1 is a chimerical protein of bacteria and eukarya. Regional analysis showed high sequence similarity to higher eukaryotic enzymes in the central and C-terminal regions which are important for catalytic activity of the enzyme. In contrast, the N-terminal portion exhibits bacterial features and does not possess the higher eukaryotic sequence which is involved in high molecular weight (HMW) complex formation. These results suggest that archaeon AspRS has a eukaryotic-type catalytic mechanism without forming the HMW complex. This is the first example which shows that an archaeal protein possesses eukaryotic and bacterial features.
对嗜热栖热菌（Pyrococcus sp.）KOD1（KOD1）编码天冬氨酰 - tRNA合成酶（AspRS）的基因进行了克隆、测序，并在大肠杆菌中表达。纯化后的AspRS对从KOD1中提取的tRNA具有氨酰化活性。对推导的氨基酸序列（438个氨基酸，50,893道尔顿）分析表明，KOD1的AspRS是一种细菌和真核生物的嵌合蛋白。区域分析显示，在对该酶催化活性很重要的中央和C末端区域，与高等真核生物酶具有高度的序列相似性。相反，N末端部分具有细菌特征，不具备参与高分子量（HMW）复合物形成的高等真核生物序列。这些结果表明，古菌AspRS具有真核生物类型的催化机制，而不形成HMW复合物。这是首次表明古菌蛋白具有真核生物和细菌特征的例子。
