摘要：

Two cytoplasmic "petite" (rho-) clones of Saccharomyces cerevisiae have been selected for the retention of the aspartic acid tRNA gene. The two clones, designated DS200/A102 and DS200/A5, have tandemly repeated segments of mitochondrial DNA (mtDNA) with unit lengths of 1,000 and 6,400 base pairs, respectively. The DS200/A102 genome has a single tRNA gene with a 3'-CUG-5' anticodon capable of recognizing the 5'-GAC-3' and 5'-GAU-3' codons for aspartic acid. The mtDNA segment of DS200/A102 has been determined to represent the wild type sequence from 5.3 to 6.8 map units. The genome of DS200/A5 is more complex encompassing the region of wild type mtDNA from 3.5 to 12.7 units. A continuous sequence has been obtained from 3.5 to 8.6 units. In addition to the aspartic acid tRNA, this region codes for the tRNAUGCAla,tRNAUCUArg, tRNAACGArg, tRNAGCUSer,tRNAUCCGly and tRNAUUULys. The DNA sequence of the DS200/A5 genome has allowed us to deduce the secondary structures of the seven tRNAs and to assign precise map positions for their genes. All the tRNAs except tRNA GUCAsp exhibit most of the invariant features of prokaryotic and eukaryotic tRNAs. The aspartic acid tRNA has unusual D and T psi C loops. The structure of this tRNA is similar to the mitochondrial initiator tRNA of Neurospora crassa (Heckman, J.E., Hecker, L.I., Shwartzbach, S.D., Barnett, W.E., Baumstark, B., and RajBhandary, U.L. Cell 13, 83-95).

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