Leehey M A, Squassoni C A, Friederich M W, Mills J B, Hagerman P J
Department of Neurology, University of Colorado Health Sciences Center, Denver 80262, USA.
Biochemistry. 1995 Dec 19;34(50):16235-9. doi: 10.1021/bi00050a001.
Transfer RNAs possess highly conserved secondary structures, and crystallographic studies suggest a common, L-shaped tertiary conformation in which the anticodon and acceptor stems are disposed at approximately right angles to one another. However, many animal mitochondrial tRNAs possess unusual secondary structures, and little is known regarding their tertiary conformations, in particular, the relative orientations of their acceptor and anticodon stems. To address this issue, we have constructed heteroduplex RNA molecules corresponding to human mitochondrial and cytoplasmic lysyl tRNAs in which the acceptor and anticodon stems of each tRNA have been extended by approximately 70 base pairs. The rotational decay times of the two "extended" tRNA(Lys) species were compared to the decay times of a linear RNA control and to an extended yeast cytoplasmic tRNA(Phe) species whose interstem angle had been reported previously. Whereas the apparent interstem angle of the human cytoplasmic tRNA(Lys) species is essentially identical to that of the yeast tRNA(Phe) heteroduplex, with both conforming to the canonical L-shape, the angle for the mitochondrial tRNA(Lys) construct is much larger (approximately 140 degrees). Thus, the universal L-shape may not be applicable to noncanonical mitochondrial tRNAs, a finding of significance for both tRNA evolution and mitochondrial disease.
转运RNA具有高度保守的二级结构，晶体学研究表明其具有一种常见的L形三级构象，其中反密码子茎和受体茎相互成大约直角排列。然而，许多动物线粒体tRNA具有不寻常的二级结构，关于它们的三级构象，特别是受体茎和反密码子茎的相对取向，人们了解甚少。为了解决这个问题，我们构建了与人类线粒体和细胞质赖氨酰tRNA相对应的异源双链RNA分子，其中每个tRNA的受体茎和反密码子茎都延伸了大约70个碱基对。将这两种“延伸”的tRNA（Lys）物种的旋转衰减时间与线性RNA对照以及一种延伸的酵母细胞质tRNA（Phe）物种的衰减时间进行比较，后者的茎间角度先前已有报道。虽然人类细胞质tRNA（Lys）物种的表观茎间角度与酵母tRNA（Phe）异源双链的基本相同，两者都符合典型的L形，但线粒体tRNA（Lys）构建体的角度要大得多（约140度）。因此，通用的L形可能不适用于非典型的线粒体tRNA，这一发现对tRNA进化和线粒体疾病都具有重要意义。
