Ito K, Uno M, Nakamura Y
Department of Tumor Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan.
Proc Natl Acad Sci U S A. 1998 Jul 7;95(14):8165-9. doi: 10.1073/pnas.95.14.8165.
Prokaryotic translational release factors, RF1 and RF2, catalyze polypeptide release at UAG/UAA and UGA/UAA stop codons, respectively. In this study, we isolated a bacterial RF2 mutant (RF2*) containing an E167K substitution that restored the growth of a temperature-sensitive RF1 strain of Escherichia coli and the viability of a chromosomal RF1/RF2 double knockout. In both in vivo and in vitro polypeptide termination assays, RF2* catalyzed UAG/UAA termination, as does RF1, as well as UGA termination, showing that RF2* acquired omnipotent release activity. This result suggests that the E167K mutation abolished the putative third-base discriminator function of RF2. These findings are interpreted as indicating that prokaryotic and eukaryotic release factors share the same anticodon moiety and that only one omnipotent release factor is sufficient for bacterial growth, similar to the eukaryotic single omnipotent factor.
原核生物翻译释放因子RF1和RF2分别在UAG/UAA和UGA/UAA终止密码子处催化多肽释放。在本研究中，我们分离出一种细菌RF2突变体（RF2*），其含有E167K取代，该取代恢复了大肠杆菌温度敏感型RF1菌株的生长以及染色体RF1/RF2双敲除菌株的活力。在体内和体外多肽终止试验中，RF2与RF1一样催化UAG/UAA终止，以及UGA终止，表明RF2获得了全能释放活性。这一结果表明E167K突变消除了RF2假定的第三碱基识别功能。这些发现被解释为表明原核生物和真核生物释放因子共享相同的反密码子部分，并且类似于真核生物的单一全能因子，仅一个全能释放因子就足以支持细菌生长。
