Kelley S O, Steinberg S V, Schimmel P
Skaggs Institute for Chemical Biology, The Scripps Research Institute, Beckman Center, La Jolla, California 92037, USA.
J Biol Chem. 2001 Apr 6;276(14):10607-11. doi: 10.1074/jbc.M008320200. Epub 2000 Dec 7.
Mutations in human mitochondrial isoleucine tRNA (hs mt tRNA(Ile)) are associated with cardiomyopathy and opthalmoplegia. A recent study showed that opthalmoplegia-related mutations gave rise to severe decreases in aminoacylation efficiencies and that the defective mutant tRNAs were effective inhibitors of aminoacylation of the wild-type substrate. The results suggested that the effectiveness of the mutations was due in large part to an inherently fragile mitochondrial tRNA structure. Here, we investigate mutant tRNAs associated with cardiomyopathy, and a series of rationally designed second-site substitutions introduced into both opthalmoplegia- and cardiomyopathy-related mutant tRNAs. A source of structural fragility was uncovered. An inherently unstable T-stem appears susceptible to misalignments. This susceptibility sensitizes both domains of the L-shaped tRNA structure to base substitutions that are deleterious. Thus, the fragile T-stem makes the structure of this human mitochondrial tRNA particularly vulnerable to local and distant mutations.
人类线粒体异亮氨酸转运RNA（hs mt tRNA(Ile)）中的突变与心肌病和眼肌麻痹相关。最近的一项研究表明，与眼肌麻痹相关的突变导致氨酰化效率严重降低，并且有缺陷的突变型转运RNA是野生型底物氨酰化的有效抑制剂。结果表明，这些突变的有效性在很大程度上归因于线粒体转运RNA固有的脆弱结构。在此，我们研究与心肌病相关的突变型转运RNA，以及一系列合理设计的引入到与眼肌麻痹和心肌病相关的突变型转运RNA中的第二位点取代。发现了结构脆弱性的一个来源。固有的不稳定T茎似乎易发生错配。这种易感性使L形转运RNA结构的两个结构域对有害的碱基取代敏感。因此，脆弱的T茎使这种人类线粒体转运RNA的结构特别容易受到局部和远距离突变的影响。
