Weixlbaumer Albert, Murphy Frank V, Dziergowska Agnieszka, Malkiewicz Andrzej, Vendeix Franck A P, Agris Paul F, Ramakrishnan V
Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
Nat Struct Mol Biol. 2007 Jun;14(6):498-502. doi: 10.1038/nsmb1242. Epub 2007 May 13.
One of the most prevalent base modifications involved in decoding is uridine 5-oxyacetic acid at the wobble position of tRNA. It has been known for several decades that this modification enables a single tRNA to decode all four codons in a degenerate codon box. We have determined structures of an anticodon stem-loop of tRNA(Val) containing the modified uridine with all four valine codons in the decoding site of the 30S ribosomal subunit. An intramolecular hydrogen bond involving the modification helps to prestructure the anticodon loop. We found unusual base pairs with the three noncomplementary codon bases, including a G.U base pair in standard Watson-Crick geometry, which presumably involves an enol form for the uridine. These structures suggest how a modification in the uridine at the wobble position can expand the decoding capability of a tRNA.
解码过程中最常见的碱基修饰之一是位于tRNA摆动位置的尿苷5-氧乙酸。几十年来人们已经知道，这种修饰使单个tRNA能够解码简并密码子盒中的所有四个密码子。我们已经确定了含有修饰尿苷的tRNA（Val）反密码子茎环的结构，其所有四个缬氨酸密码子位于30S核糖体亚基的解码位点。涉及该修饰的分子内氢键有助于预构象化反密码子环。我们发现了与三个非互补密码子碱基形成的异常碱基对，包括具有标准沃森-克里克几何结构的G·U碱基对，这可能涉及尿苷的烯醇形式。这些结构揭示了摆动位置尿苷的修饰如何扩展tRNA的解码能力。
