Kumazawa Y, Himeno H, Miura K, Watanabe K
Department of Biological Sciences, Tokyo Institute of Technology, Kanagawa.
J Biochem. 1991 Mar;109(3):421-7. doi: 10.1093/oxfordjournals.jbchem.a123397.
The present study shows unilateral aminoacylation specificity between bovine mitochondria and eubacteria (Escherichia coli and Thermus thermophilus) in five amino acid-specific aminoacylation systems. Mitochondrial synthetases were capable of charging eubacterial tRNA as well as mitochondrial tRNA, whereas eubacterial synthetases did not efficiently charge mitochondrial tRNA. Mitochondrial phenylalanyl-, threonyl-, arginyl-, and lysyl-tRNA synthetases were shown to charge and discriminate cognate E. coli tRNA species from noncognate ones strictly, as did the corresponding E. coli synthetases. By contrast, mitochondrial seryl-tRNA synthetase not only charged cognate E. coli serine tRNA species but also extensively misacylated noncognate E. coli tRNA species. These results suggest a certain conservation of tRNA recognition mechanisms between the mitochondrial and E. coli aminoacyl-tRNA synthetases in that anticodon sequences are most likely to be recognized by the former four synthetases, but not sufficiently by the seryl-tRNA synthetase. The unilaterality in aminoacylation may imply that tRNA recognition mechanisms of the mitochondrial synthetases have evolved to be, to some extent, simpler than their eubacterial counterparts in response to simplifications in the species-number and the structural elements of animal mitochondrial tRNAs.
本研究表明，在五个氨基酸特异性氨酰化系统中，牛线粒体与真细菌（大肠杆菌和嗜热栖热菌）之间存在单向氨酰化特异性。线粒体合成酶能够使真细菌tRNA以及线粒体tRNA氨酰化，而真细菌合成酶不能有效地使线粒体tRNA氨酰化。线粒体苯丙氨酰 - 、苏氨酰 - 、精氨酰 - 和赖氨酰 - tRNA合成酶能够严格地使大肠杆菌同源tRNA种类氨酰化，并将其与非同源tRNA种类区分开来，相应的大肠杆菌合成酶也是如此。相比之下，线粒体丝氨酰 - tRNA合成酶不仅能使大肠杆菌同源丝氨酸tRNA种类氨酰化，还能使大量非同源大肠杆菌tRNA种类错误氨酰化。这些结果表明，线粒体和大肠杆菌氨酰 - tRNA合成酶之间在tRNA识别机制上存在一定的保守性，即前四种合成酶最有可能识别反密码子序列，但丝氨酰 - tRNA合成酶则不能充分识别。氨酰化的单向性可能意味着，线粒体合成酶的tRNA识别机制已经进化得在某种程度上比其真细菌对应物更简单，以应对动物线粒体tRNA种类数量和结构元件的简化。
