转移RNA结构基因共有序列的统计分析

本文以大肠杆菌、地钱叶绿体和鸡线粒体基因组中:RNA结构基因的全部拷贝数为分析总体,统计出了碱基分布。在大肠杆菌中证实了Pu52-Py62半不变核苷酸对,排除了A21的共有性,确认了24个共有核苷酸,其中半数核苷酸参加三级氢键的形成作用;螺旋区碱基标准配对率平均为95％;在非标准配对中以GU为主而且集中在两个连续双螺旋的缺口处,又发现在第10、27、49位G居多现象,其意义有待阐明。大肠杆菌tRNA序列与地钱叶绿体tRNA序列极为相似,鸡线粒体tRNA由于缺乏典型的D环和TψC环而与大肠杆菌tRNA序列差别较大。本文还计算了大肠杆菌tRNA基因拷贝数与密码子利用率之间相关系数(r=0.976),并讨论了影响细胞内tRNA含量的基因剂量效应,位置效应诸问题。

Statistical Analysis of Conserved Sites in the Structural Genes of tRNA

The base distribution in the structural genes of tRNA for Escherichia coli K12, the liverwort (Marchanta polymorpha) chloroplast and the chicken mitochondrial genome are obtained by stastisti- cal analysis. Analysis for E. coli reveals 24 conserved nucleotides, half of which are attributed to form tertiary hydrogen bounds; the average percentage of standard base-pairing in four stems of tRNA is 95%; among the non-standard base-pairing, the overwhelming majority is GU and it is concentrated in the region of gaps of two continuous double helixes and G is preferred to dominance at 10,27,49 sites. The tRNA sequences of E. coli show the excellent similarities with that of liverwort chloropolast than the chicken mitochondrial. The correlation coefficient between the copy numbers of tRNA genes and the codon usages in E. coli is calculated (r=0. 976) and it is exhibited a good correspondence be- tween them.