Seit-Nebi Alim, Frolova Ludmila, Kisselev Lev
Engelhardt Institute of Molecular Biology, Moscow, Russia.
EMBO Rep. 2002 Sep;3(9):881-6. doi: 10.1093/embo-reports/kvf178. Epub 2002 Aug 16.
In eukaryotic ribosomes, termination of translation is triggered by class 1 polypeptide release factor, eRF1. In organisms with a universal code, eRF1 responds to three stop codons, whereas, in ciliates with variant codes, only one or two codon(s) remain(s) as stop signals. By mutagenesis of the Y-C-F minidomain of the N domain, we converted an omnipotent human eRF1 recognizing all three stop codons into a unipotent 'ciliate-like' UGA-only eRF1. The conserved Cys127 located in the Y-C-F minidomain plays a critical role in stop codon recognition. The UGA-only response has also been achieved by concomitant substitutions of four other amino acids located at the Y-C-F and NIKS minidomains of eRF1. We suggest that for eRF1 the stop codon decoding is of a non-linear (non-protein-anticodon) type and explores a combination of positive and negative determinants. We assume that stop codon recognition is profoundly different by eukaryotic and prokaryotic class 1 RFs.
在真核生物核糖体中，翻译的终止由1类多肽释放因子eRF1触发。在使用通用密码子的生物体中，eRF1对三个终止密码子作出反应，而在具有可变密码子的纤毛虫中，只有一个或两个密码子作为终止信号保留下来。通过对N结构域的Y-C-F小结构域进行诱变，我们将识别所有三个终止密码子的全能人类eRF1转化为只识别UGA的“类纤毛虫”单能eRF1。位于Y-C-F小结构域的保守半胱氨酸127在终止密码子识别中起关键作用。通过同时替换位于eRF1的Y-C-F和NIKS小结构域的其他四个氨基酸，也实现了仅对UGA的反应。我们认为，对于eRF1来说，终止密码子解码是非线性（非蛋白质-反密码子）类型的，并探索了正负决定因素的组合。我们假设真核生物和原核生物的1类释放因子对终止密码子的识别有很大不同。
