Yeast mitochondrial DNA specifies tRNA for 19 amino acids. Deletion mapping of the tRNA genes

Abstract

Previously identified were 14 aminoacyl-tRNA that were specified by yeast mitochondrial DNA (mtDNA). Four more amino acids (Arg, Cys, Trp, Thr) that acylate tRNA which hybridize with mtDNA are reported. Furthermore, 1 of the 2 mitochondrial tRNA that earlier were demonstrated to be directly charged with glutamic acid responds to glutamine but not to glutamic acid codons. Thus, Gln-tRNAGln appears to be formed by transamidation of a missense intermediate Glu-tRNAGln. This brings to 19 the number of amino acids which have corresponding tRNA specified by mtDNA. Only tRNAAsn was not yet shown to be a mtDNA transcript. The genes for the newly identified mitochondrial tRNA were mapped as well as several others that were previously identified but unmapped, by hybridization to the mtDNA of a series of petite deletion mutants. Now 20 mitochondrial tRNA genes (including 2 methionyl-tRNA) are ordered with respect to the antibiotic resistance markers chloramphenicol (CR), erythromycin (ER), paromomycin (PR) and oligomycin I and II (ORI, ORII). Eighteen tRNA genes map between the C and E resistance markers. Only the serinyl-tRNA and glutamyl-tRNA genes are localized near the OI and OII resistance markers.