Intermolecular Network specific for mitochondrial translation systems and its functional characteristics

与原核生物相比，动物线粒体的遗传信息翻译系统具有以下显著特点。(1)线虫线粒体中存在T臂缺失的tRNA和具有较长C末端的特异性翻译因子EF-Tu，识别这种类型的tRNA。(2)存在氨酰-tRNA合成酶，可识别所有类型的tRNA，不依赖于物种，包括tRNAs。(3)线粒体核糖体与线虫核糖体在功能上是相同的，尽管RNA和蛋白质含量的比例相反。大肠杆菌核糖体中RNA与蛋白质的含量之比为2：1，动物线粒体中为1：3。通过分子间网络的分析，探讨了构成生命现象根源的遗传信息翻译系统的构建原理，得到以下结果：(1)线虫Mitochondri…中存在两种Ef-Tu还有一个(EF-Tu1)识别T臂缺失的tRNA，另一个(EF-Tu2)识别D臂缺失的Seryl-tRNA。EF-Tu1不仅识别tRNA结构，还识别附着在tRNA上的丝氨酸残基。对识别过程中涉及的氨基酸残基进行了鉴定。在缺乏T臂的tRNA中普遍存在的m^1A9残基是tRNA与EF-Tu1结合所必需的。(2)线粒体丝氨酸-tRNA合成酶识别两种结构不同的丝氨酸tRNA。该酶在总结构上与大肠杆菌非常相似，但在N端有一个α-螺旋区，在C端有一个尾区，这两个结构域在识别D茎缺失的丝氨酸tRNA中具有不可或缺的作用。由于识别两种不同结构的tRNA所涉及的氨基酸残基有明显的差异，推测该酶识别这两种类型的tRNA的方式有很大的不同(双重模式识别)。(3)线粒体(Mt)EF-G可以作用于大肠杆菌核糖体，而大肠杆菌EF-G不能作用于线粒体核糖体。结果表明，这种差异仅源于核糖体的一种茎蛋白L7/L12的差异。较少

The genetic information translation system of animal mitochondria possesses the following remarkable characteristics as compared with that of prokaryote. (1) There exist T arm-lacking tRNA and a specific translation factor EF-Tu with a long C terminal region, recognizing this type of tRNA in nematode mitochondria. (2) There exist aminoacyl-tRNA synthetases which recognize all types of tRNA independent of the species including the tRNAs. (3) Mitochondrial ribosomes are functionally equivalent to E. coil ribosomes, although the ratio of content of RNAs and proteins is reversed. ; the ratio of content of RNAs and proteins is 2:1 in E. coliribosomes and that of animal mitochondria is 1:3. Through analyses of intermolecular network of these components, the construction principal of the genetic information translation system, which constitutes the root of the living phenomena, was investigated, and the following results were obtained.(1) There exist 2 species of EF-Tu in nematode mitochondri … More a, one (EF-Tu1) recognizing the T arm-lacking tRNA, the other (EF-Tu2 ) recognizing the D arm-lacking seryl-tRNA. EF-Tu1 recognizes not only tRNA structure but also serine residue attached to the tRNA. The amino acid residues involved in these recognitions were identified. The m^1A9 residue commonly existing in the T-arm-lacking tRNAs is indispensable for the binding of tRNA to EF-Tu1.(2) Mitochondrial seryl-tRNA synthetases recognize 2 structurally different serine tRNAs. The enzyme is very similar to that of E. coli in a total structure, but possesses extra two domains, an α-helical region at the N terminal and a tail region at the C terminal These two domains possess indispensable role in recognizing the D stem-lacking serine tRNA. Since a clear difference has been observed in amino acid residues involved in recognition of 2 structurally different tRNAs, it was deduced that this enzyme recognizes these 2 types of tRNA by quite different manner (dual mode recognition).(3) Mitochondrial (mt) EF-G can function on E. coli ribosome, on the other hand, E. coli EF-G cannot function on mitochondrial ribosome. It turned out that the difference was originated in the difference in only a stalk protein of ribosome, L7/L12. Less