RNA molecules of all species contain modified nucleotides and particularly m5U residues. The vertebrate mitochondrial small subunit rRNA contains m5U nucleotide in a unique site. In this work we found an enzyme, TRMT2B, responsible for the formation of this nucleotide and m5U residues in a number of mitochondrial tRNA species. Inactivation of the Trmt2B gene leads to a reduction of the activity of respiratory chain complexes I, III and IV, containing the subunits synthesized by the mitochondrial protein synthesis apparatus. Comparative sequence analysis of m5U-specific RNA methyltransferases revealed an unusual evolutionary pathway of TRMT2B formation which includes consecutive substrate specificity switches from the large subunit rRNA to tRNA and then to the small subunit rRNA.

中文翻译：

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小鼠Trmt2B蛋白是双重特异性线粒体甲基转移酶，负责在tRNA和rRNA中形成m5U。

所有物种的RNA分子均包含修饰的核苷酸，尤其是m5U残基。脊椎动物线粒体小亚基rRNA在唯一位点包含m5U核苷酸。在这项工作中，我们发现了一种酶TRMT2B，该酶负责在许多线粒体tRNA物种中形成该核苷酸和m5U残基。Trmt2B基因失活导致呼吸链复合物I，III和IV的活性降低，其中包含由线粒体蛋白质合成设备合成的亚基。对m5U特异性RNA甲基转移酶的比较序列分析揭示了TRMT2B形成的异常进化途径，包括从大亚基rRNA到tRNA，再到小亚基rRNA的连续底物特异性转换。