Tomita Kozo, Weiner Alan M
Department of Biochemistry, University of Washington School of Medicine, Seattle 98195-7350, USA.
J Biol Chem. 2002 Dec 13;277(50):48192-8. doi: 10.1074/jbc.M207527200. Epub 2002 Oct 4.
The 3'-terminal CCA sequence of tRNA is faithfully constructed and repaired by the CCA-adding enzyme (ATP(CTP):tRNA nucleotidyltransferase) using CTP and ATP as substrates but no nucleic acid template. Until recently, all CCA-adding enzymes from all three kingdoms appeared to be composed of a single kind of polypeptide with dual specificity for adding both CTP and ATP; however, we recently found that in Aquifex aeolicus, which lies near the deepest root of the eubacterial 16 S rRNA-based phylogenetic tree, CCA addition represents a collaboration between closely related CC-adding and A-adding enzymes (Tomita, K. and Weiner, A. M. (2001) Science 294, 1334-1336). Here we show that in Synechocystis sp. and Deinococcus radiodurans, as in A. aeolicus, CCA is added by homologous CC- and A-adding enzymes. We also find that the eubacterial CCA-, CC-, and A-adding enzymes, as well as the related eubacterial poly(A) polymerases, each fall into phylogenetically distinct groups derived from a common ancestor. Intriguingly, the Thermatoga maritima CCA-adding enzyme groups with the A-adding enzymes, suggesting that these distinct tRNA nucleotidyltransferase activities can intraconvert over evolutionary time.
tRNA的3'-末端CCA序列是由CCA添加酶（ATP(CTP):tRNA核苷酸转移酶）以CTP和ATP为底物、无需核酸模板精确构建和修复的。直到最近，来自所有三个生物界的所有CCA添加酶似乎都由一种对添加CTP和ATP具有双重特异性的单一多肽组成；然而，我们最近发现，在基于真细菌16S rRNA的系统发育树根部附近的嗜热栖热菌中，CCA的添加是由密切相关的CC添加酶和A添加酶协同完成的（富田，K.和韦纳，A.M.（2001年）《科学》294，1334 - 1336）。在这里我们表明，与嗜热栖热菌一样，在集胞藻属和耐辐射球菌中，CCA是由同源的CC添加酶和A添加酶添加的。我们还发现，真细菌的CCA添加酶、CC添加酶和A添加酶，以及相关的真细菌聚腺苷酸聚合酶，各自都属于从一个共同祖先衍生而来的系统发育上不同的组。有趣的是，嗜热栖热放线菌的CCA添加酶与A添加酶归为一组，这表明这些不同的tRNA核苷酸转移酶活性在进化过程中可以相互转化。
