A cluster of six tRNA genes inDrosophilamitochondrial DNA that includes a gene for an unusual tRNA^ser_AGY

Abstract

Genes for URF3, tRNAala, tRNAarg, tRNAasn, tRNASer, tRNA1u, tRNAphe, and the carboxyl terminal segment of the URF5 gene have een identified within a sequenced segment of the mtDNA molecule of Drosophila yakuba. The genes occur in the order given. The URF5 and tRNAPhe genes are transcribed in the same direction as replication while the URF3 and remaining five tRNA genes are transcribed in the opposite direction. Considerable differences exist in the relative arrangement of these genes in D. yakuba and mammalian mtDNA molecules. In the tRNAser gene an eleven nucleotide loop, within which secondary structure formation seems unlikely, replaces the dihydrouridine am, and both the variable loop (six nucleotides) and the TPC loop (nine nucleotides) are larger than in any other D. yakuba tRNA gene. As available evidence is consistent with AGA codons specifying serine rather than arginine in the Drosophila mitochondrial genetic code, the possibility is considered that the 5GU anticodon of the D. yakuba tRNAser gene can recognize AGA as well as AGY codons.

RNA mapping onDrosophilamitochondrial DNA: precursors and template strands

“…Twelve major RNAs were identified, eleven poly (A)+ (RNAs 1-9,11, 13) and one poly (A) (RNA 10) , ranging in size from 1.8 to 0.35 Kb. We also detected 28 other RNA species (RNAs a-z, 12) ranging in size from 0.22 Kb to over 3.2 Kb.…”

“…Dash indicates mtDNA. The standards were a mixture of various mtDNA fragments calibrated in our electrophoretic conditions with E coli rRNAs as 2.9, 2.0, 0.88, 0.58, 0.4 Kb.11 (Middle))-Location of genes and direction of transcription, as determined by sequencing of the a aube mtDNA (6,(8)(9)(10)(11)(12)(13).…”

“…The a yaitub mtDNA has bean completely squenced (6,(8)(9)(10)(11)(12)(13)56) and differs mostly from V me/ar~wter mtDNA by the size of the A+T rich region. The a yaktia mtDNA encodes for the same genes as those found in higher organism's mtDNA (14)(15)(16)(17), i.e., 2 rRNA and 22 tRNA genes, 13 significant reading frames coding for cytochrome b (cyt.b), cytochrome c oxidase subunits I, 11, III (Co 1, Co 11, Co 111), ATPase subunits 6 and 8, seven subunits of NADH deshydrogenase (ND 1-6) (18-21 ,57).…”

Mediterranean fruit fly, Ceratitis capitata (Wiedemann), mitochondrial DNA: genes and secondary structures for six t‐RNAs

“…However, the substitutions made still allow the necessary tertiary interactions to permit stacking of the TVC and dihydrouridine loops. For t-RNAPhe, the TTC loop is smaller in C. capitata, while for t-RNAG'" the C. capitata dihydrouridine loop contains one more base and the TVC loop one less (Clary & Wolstenholme, 1984).…”

“…Such truncated t-RNASer forms have been found in all animal mitochondrial t-RNAs sequenced (Garesse, 1988). Finally, with the exception of a substitution of a C for a G in t-RNAPhe, the anticodon loops are completely conserved with respect to D. yakuba (Clary & Wolstenholme, 1984).…”