Yamada Yuko, Matsugi Jitsuhiro, Ishikura Hisayuki, Murao Katsutoshi
Department of Biochemistry, Jichi Medical School, 3311-1 Yakushiji, Minamikawachi-machi, Tochigi-ken, 329-0498, Japan.
Biochim Biophys Acta. 2005 May 1;1728(3):143-9. doi: 10.1016/j.bbaexp.2005.02.011. Epub 2005 Mar 22.
In Bacillus subtilis, four codons, CCU, CCC, CCA, and CCG, are used for proline. There exists, however, only one proline-specific tRNA having the anticodon mo(5)UGG. Here, we found that this tRNA(Pro)(mo(5)UGG) can read not only the codons CCA, CCG and CCU but also CCC, using an in vitro assay system. This means that the first nucleoside of its anticodon, 5-methoxyuridine (mo(5)U), recognizes A, G, U and C. On the other hand, it was reported that mo(5)U at the first position of the anticodon of tRNA(Val)(mo(5)UAC) can recognize A, G, and U but not C. A comparison of the structure of the anticodon stem and loop of tRNA(Pro)(mo(5)UGG) with those of other tRNAs containing mo(5)U at the first positions of the anticodons suggests that a modification of nucleoside 32 to pseudouridine (Psi) enables tRNA(Pro)(mo(5)UGG) to read the CCC codon.
在枯草芽孢杆菌中，脯氨酸由四个密码子CCU、CCC、CCA和CCG编码。然而，只有一种具有反密码子mo(5)UGG的脯氨酸特异性tRNA。在此，我们利用体外分析系统发现，这种tRNA(Pro)(mo(5)UGG)不仅能识别密码子CCA、CCG和CCU，还能识别CCC。这意味着其反密码子的第一个核苷5-甲氧基尿苷（mo(5)U）能识别A、G、U和C。另一方面，据报道，tRNA(Val)(mo(5)UAC)反密码子第一位的mo(5)U能识别A、G和U，但不能识别C。将tRNA(Pro)(mo(5)UGG)反密码子茎环结构与反密码子第一位含有mo(5)U的其他tRNA的结构进行比较，结果表明，核苷32修饰为假尿苷（Ψ）可使tRNA(Pro)(mo(5)UGG)识别CCC密码子。
