Lee C C, Craigen W J, Muzny D M, Harlow E, Caskey C T
Institute for Molecular Genetics, Baylor College of Medicine, Houston, TX 77030.
Proc Natl Acad Sci U S A. 1990 May;87(9):3508-12. doi: 10.1073/pnas.87.9.3508.
The termination of protein synthesis is encoded by in-frame nonsense (stop) codons. Most organisms use three nonsense codons: UGA, UAG, and UAA. In contrast to sense codons, which are decoded by specific tRNAs, nonsense codons are decoded by proteins called release factors (RFs). Here we report the cloning of a mammalian RF cDNA by the use of monoclonal antibodies specific for rabbit RF. Functional studies showed that, when expressed in Escherichia coli, the protein encoded by this cDNA has in vitro biochemical characteristics similar to those of previously characterized mammalian RFs. DNA sequencing of this eukaryotic RF cDNA revealed a remarkable sequence similarity to bacterial and mitochondrial tryptophanyl-tRNA synthetases, with the greatest similarity confined to the synthetase active site, and no obvious similarity to bacterial RFs.
蛋白质合成的终止由读框内的无义（终止）密码子编码。大多数生物体使用三个无义密码子：UGA、UAG和UAA。与由特定tRNA解码的有义密码子不同，无义密码子由称为释放因子（RF）的蛋白质解码。在此，我们报告通过使用针对兔RF的单克隆抗体克隆了一个哺乳动物RF cDNA。功能研究表明，当在大肠杆菌中表达时，该cDNA编码的蛋白质具有与先前表征的哺乳动物RF相似的体外生化特性。对该真核RF cDNA的DNA测序揭示了与细菌和线粒体色氨酰-tRNA合成酶具有显著的序列相似性，最大相似性局限于合成酶活性位点，并且与细菌RF没有明显的相似性。
