Simoneau P, Li C M, Loechel S, Wenzel R, Herrmann R, Hu P C
Department of Pediatrics, University of North Carolina, Chapel Hill 27599.
Nucleic Acids Res. 1993 Oct 25;21(21):4967-74. doi: 10.1093/nar/21.21.4967.
The 33 genes encoding the complete set of tRNA species in Mycoplasma pneumoniae have been cloned and sequenced. They are organized into 5 clusters in addition to 9 single genes. No redundant gene was found, indicating that 33 tRNAs correspond to 32 different anticodons and decode all 62 codons used in this organism. There is only one single tRNA for each of the Ala, Leu, Pro, and Val family boxes. Therefore, a simplified decoding system resembling that recently described for Mycoplasma capricolum (1) has to also exist in M.pneumoniae. However, analysis of the anticodon set and codon usage revealed features characteristic of the latter: (i) there is no obvious preference toward AT rich synonymous codons, (ii) CGG codons are assigned for arginine and are translated by tRNA Arg(UCG), and (iii) CNN or GNN anticodons are encountered in the Ser, Thr, Arg, and Gly family boxes. We thus propose that this codon-anticodon recognition pattern has emerged in the 'M.pneumoniae cluster' under a genomic economization strategy but without the influence of AT pressure.
肺炎支原体中编码全套tRNA种类的33个基因已被克隆和测序。它们除9个单基因外，还被组织成5个簇。未发现冗余基因，这表明33种tRNA对应32种不同的反密码子，并解码该生物体中使用的所有62种密码子。丙氨酸、亮氨酸、脯氨酸和缬氨酸家族框中的每一个都只有一种tRNA。因此，类似于最近描述的山羊支原体（1）的简化解码系统也必定存在于肺炎支原体中。然而，对反密码子集和密码子使用情况的分析揭示了后者的特征：（i）对富含AT的同义密码子没有明显偏好，（ii）CGG密码子被指定用于精氨酸，并由tRNA Arg(UCG)翻译，（iii）在丝氨酸、苏氨酸、精氨酸和甘氨酸家族框中遇到CNN或GNN反密码子。因此，我们提出这种密码子-反密码子识别模式是在基因组节约策略下于“肺炎支原体簇”中出现的，但不受AT压力的影响。
