期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1979
卷号：76
期号：12
页码：6534-6538
DOI：10.1073/pnas.76.12.6534
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A mitochondrial mutation that genetically maps in the middle of the gene coding cytochrome c oxidase subunit II has been found to be a single-base-pair deletion. Three independently isolated spontaneous revertants of this mutant have different single-base-pair insertions within 15 nucleotides of the mutation. These findings clearly identify the location of the gene and suggest that the mutation causes a frame-shift. The sequence of about 900 base pairs surrounding the mutation has been determined and found to have several chain termination codons in every possible reading frame. The sequence can, however, be translated in one frame by assuming that the codon TGA does not cause chain termination in yeast mitochondira, as was recently suggested for the human organelle [Barrell, B. G., Bankier, A. T. & Drouin, J. (1979) Nature (London), in press]. If TGA codes for tryptophan residues, as is apparently the case in human mitochondria, a polypeptide can be read from the yeast mtDNA that is identical to bovine cytochrome oxidase subunit II at 37.8% of its residues. Furthermore, the DNA sequences of the frame-shift revertants discussed above predict relative isolectric point differences between the wild-type and various revertant forms of the polypeptide. The detection of these isolectric point differences by two-dimensional electrophoresis of subunit II from the various strains independently confirms the presumed reading frame of the gene. It is concluded that TGA is translated in yeast mitochondria, most probably as tryptophan.
关键词：frame-shift revertants ; DNA sequence ; genetic code ; protein sequence homology
