Chechetkin V R
Biochip Centre at Engelhardt Institute of Molecular Biology, Vavilov str., 32, Moscow 119991, Russia.
J Theor Biol. 2006 Oct 21;242(4):922-34. doi: 10.1016/j.jtbi.2006.05.008. Epub 2006 May 22.
The possible codon-anticodon pairings follow the standard genetic code, yet in a different mode. The corresponding rules for decoding sequence of the codons in mRNA with tRNA may be called "tRNA code". In this paper we analyse the mutational and translational stability of such tRNA code. Our approach is based on the model of "ambiguous intermediate" and on the study of underlying block structure and Eulerean graph technique. It is shown that the wobble rules and the reduced number of tRNA anticodons strongly affect the mutational and translational stability of the code. The selection of tRNA anticodons, besides the optimization of translation, also ensures the more reliable start and, to a lesser extent, the stop of translation. The attribution of tRNA anticodons to the groups [WWW, WWS, SWW, SWS] and [SSS, SSW, WSS, WSW] as well as [MMM, MMK, KMM, KMK] and [KKK, KKM, MKK, MKM] clearly correlates with class I and class II aminoacyl-tRNA synthetases and obeys the principle of the optimal coding in both cases. Both W-S and M-K groupings also refer to the encoding of amino acids with the large and small side-chain volumes, which may provide such an attribution. The higher variability of tRNA code agrees with the suggestions that the variations in an assignment of tRNA anticodons may serve as the driving force generating the different variants of the genetic code.
可能的密码子 - 反密码子配对遵循标准遗传密码，但方式不同。用tRNA解码mRNA中密码子序列的相应规则可称为“tRNA密码”。在本文中，我们分析了这种tRNA密码的突变稳定性和翻译稳定性。我们的方法基于“模糊中间体”模型以及对底层块结构和欧拉图技术的研究。结果表明，摆动规则和tRNA反密码子数量的减少强烈影响密码的突变稳定性和翻译稳定性。tRNA反密码子的选择除了优化翻译外，还确保了更可靠的起始，并在较小程度上确保了翻译的终止。将tRNA反密码子归为[WWW, WWS, SWW, SWS]和[SSS, SSW, WSS, WSW]组以及[MMM, MMK, KMM, KMK]和[KKK, KKM, MKK, MKM]组，这与I类和II类氨酰 - tRNA合成酶明显相关，并且在两种情况下都遵循最佳编码原则。W - S和M - K分组也涉及具有大、小侧链体积的氨基酸编码，这可能提供了这种归属。tRNA密码的较高变异性与以下观点一致，即tRNA反密码子分配的变化可能是产生遗传密码不同变体的驱动力。
