Martin N C, Pham H D, Underbrink-Lyon K, Miller D l, Donelson J E
Nature. 1980 Jun 19;285(5766):579-81. doi: 10.1038/285579a0.
DNA sequence analysis of mitochondrial genes that code for some mitochondrial proteins has suggested that the opal terminator, UGA, is used as a sense codon in mitochondria. The complete sequences of both the yeast and human genes coding for cytochrome oxidase subunit II contain UGA codons in the reading frame. When the protein sequences predicted by these DNA sequences are compared with the known protein sequence of bovine mitochondrial cytochrome oxidase subunit II, there are regions of homology, in which UGA codons correspond to tryptophan residues. Therefore it has been suggested that UGA specifies tryptophan in the mitochondrial code. We have isolated a yeast mitochondrial tRNATrp and used it to locate the mitochondrial tRNATrp gene in pBR322-mitochondrial DNA recombinants. DNA sequence analysis of this gene revealed that the mitochondrial tRNATrp anticodon is 5'UCA3'. Because there is a U in the wobble position, this tRNA can recognize and insert tryptophan into a growing polypeptide chain in response to the nonsense codon UGA.
对编码某些线粒体蛋白质的线粒体基因进行的DNA序列分析表明，乳白终止密码子UGA在线粒体中被用作有义密码子。酵母和人类编码细胞色素氧化酶亚基II的基因的完整序列在阅读框中都含有UGA密码子。当将这些DNA序列预测的蛋白质序列与牛线粒体细胞色素氧化酶亚基II的已知蛋白质序列进行比较时，存在同源区域，其中UGA密码子对应于色氨酸残基。因此，有人提出UGA在线粒体密码中指定色氨酸。我们分离出了一种酵母线粒体tRNATrp，并利用它在pBR322-线粒体DNA重组体中定位线粒体tRNATrp基因。对该基因的DNA序列分析表明，线粒体tRNATrp反密码子是5'UCA3'。由于摆动位置有一个U，这种tRNA可以识别无义密码子UGA，并将色氨酸插入正在生长的多肽链中。
