Canaday J, Dirheimer G, Martin R P
Nucleic Acids Res. 1980 Apr 11;8(7):1445-57. doi: 10.1093/nar/8.7.1445.
Two methionine tRNAs from yeast mitochondria have been purified. The mitochondrial initiator tRNA has been identified by formylation using a mitochondrial enzyme extract. E. coli transformylase however, does not formylate the yeast mitochondrial initiator tRNA. The sequence was determined using both 32P-in vivo labeled and 32P-end labeled mt tRNAf(Met). This tRNA, unlike N. crassa mitochondrial tRNAf(Met), has two structural features typical of procaryotic initiator tRNAs: (i) it lacks a Watson-Crick base-pair at the end of the acceptor stem and (ii) has a T-psi-C-A sequence in loop IV. However, both yeast and N. crassa mitochondrial initiator tRNAs have a U11:A24 base-pair in the D-stem unlike procaryotic initiator tRNAs which have A11:U24. Interestingly, both mitochondrial initiator tRNAs, as well as bean chloroplast tRNAf(Met), have only two G:C pairs next to the anticodon loop, unlike any other initiator tRNA whatever its origin. In terms of overall sequence homology, yeast mitochondrial tRNA(Met)f differs from both procaryotic or eucaryotic initiator tRNAs, showing the highest homology with N. crassa mitochondrial initiator tRNA.
已从酵母线粒体中纯化出两种甲硫氨酸tRNA。利用线粒体酶提取物通过甲酰化作用鉴定出线粒体起始tRNA。然而，大肠杆菌转甲酰酶不能使酵母线粒体起始tRNA甲酰化。使用体内32P标记和32P末端标记的线粒体tRNAf(Met)测定了其序列。与粗糙脉孢菌线粒体tRNAf(Met)不同，这种tRNA具有原核起始tRNA的两个典型结构特征：(i) 其受体茎末端缺乏沃森-克里克碱基对，(ii) 在环IV中有T-ψ-C-A序列。然而，酵母和粗糙脉孢菌线粒体起始tRNA在D茎中都有U11:A24碱基对，这与具有A11:U24的原核起始tRNA不同。有趣的是，线粒体起始tRNA以及菜豆叶绿体tRNAf(Met)在反密码子环旁边都只有两个G:C对，这与其他任何来源的起始tRNA都不同。就整体序列同源性而言，酵母线粒体tRNA(Met)f与原核或真核起始tRNA都不同，与粗糙脉孢菌线粒体起始tRNA的同源性最高。
