tRNA molecules have well-defined sequence conservations that reflect the conserved tertiary pairs maintaining their architecture and functions during the translation processes. An analysis of aligned tRNA sequences present in the GtRNAdb data base (The Lowe Lab, University of California, Santa Cruz) led to surprising conservations on some cytosolic tRNAs specific for Alanine compared to other tRNA species, including tRNAs specific for Glycine. First, besides the well-known G3oU70 base pair in the amino acid stem, there is the frequent occurrence of a second wobble pair at G30oU40, a pair overwhelmingly observed as a Watson-Crick pair throughout phylogeny. Secondly, the tertiary pair R15/Y48 occurs as a purine-purine R15/A48 pair. Finally, the conserved T54/A58 pair maintaining the fold of the T-loop is observed as a purine-purine A54/A58 pair. The R15/A48 and A54/A58 pairs always occur together. The G30oU40 pair occurs alone or together with these other two pairs. The pairing variations are observed to variable extent depending on phylogeny. Among eukaryotes, insects display simultaneously all variations, while mammals present either the G30oU40 pair or both R15/A48 and A54/A58. tRNAs with the anticodon 34A(I)GC36 are the most prone to display all those pair variations in mammals and insects. tRNAs with anticodon Y34GC36 have preferentially G30oU40 only. These unusual pairs are not observed in bacterial, or archaeal tRNAs, probably because of the avoidance of A34-containing anticodons in 4-codon boxes. Among eukaryotes, these unusual pairing features were not observed in fungi and nematodes. These unusual structural features may affect transcription rates (e.g. 54/58) or ribosomal translocation (30/40).

中文翻译：

---

真核tRNA-Ala中不寻常的三级对

tRNA 分子具有明确定义的序列保守性，反映了在翻译过程中保持其结构和功能的保守三级对。对 GtRNAdb 数据库（Lowe 实验室，加州大学圣克鲁斯分校）中存在的对齐 tRNA 序列的分析导致与其他 tRNA 物种（包括甘氨酸特异性 tRNA）相比，某些对丙氨酸具有特异性的胞质 tRNA 具有惊人的保守性。首先，除了氨基酸茎中众所周知的 G3oU70 碱基对之外，在 G30oU40 处还经常出现第二个摆动对，这对在整个系统发育过程中被普遍观察为 Watson-Crick 对。其次，三级对 R15/Y48 以嘌呤-嘌呤 R15/A48 对的形式出现。最后，维持 T 环折叠的保守 T54/A58 对被观察为嘌呤-嘌呤 A54/A58 对。R15/A48 和 A54/A58 对总是一起出现。G30oU40 对单独出现或与其他两对一起出现。取决于系统发育，在不同程度上观察到配对变化。在真核生物中，昆虫同时表现出所有变异，而哺乳动物表现出 G30oU40 对或 R15/A48 和 A54/A58。带有反密码子 34A(I)GC36 的 tRNA 最容易在哺乳动物和昆虫中显示所有这些对变异。具有反密码子 Y34GC36 的 tRNA 仅优先具有 G30oU40。在细菌或古细菌 tRNA 中没有观察到这些不寻常的对，可能是因为在 4 密码子盒中避免了包含 A34 的反密码子。在真核生物中，在真菌和线虫中没有观察到这些不寻常的配对特征。这些不寻常的结构特征可能会影响转录率（例如