RESUMEN
We have determined the primary sequence and modification status of a transfer RNA from mosquito mitochondria whose GCU anticodon indicates that it is a serine tRNA (tRNASerGCU), and have obtained information on higher order structure using partial digestion with nucleases S1 and T1 under non-denaturing conditions. Although its primary sequence homology to mammalian mitochondrial tRNASerGCU is modest (46%), the mosquito tRNA resembles its mammalian mitochondrial counterpart in that a plausible secondary structure configuration includes a drastically abbreviated D arm and a sex base-pair anticodon stem. Other unusual features include a ribose-methylated cytidine residue at the end of the anticodon stem, and the likely occurrence of a psi residue between the amino acid arm and arm IV.
Asunto(s)
Aedes/genética , Aminoacil-ARN de Transferencia , Aedes/análisis , Animales , Secuencia de Bases , Electroforesis en Gel de Poliacrilamida , Mitocondrias/análisis , Conformación de Ácido NucleicoRESUMEN
The 3'-terminal sequence of the large ribosomal subunit ("17S") RNA of hamster mitochondria has been examined by means of oligonucleotide fingerprint analysis of 3' end-labeled samples. Patterns from partial acid or alkaline hydrolysates indicated marked heterogeneity and suggested an array of termini that included GGUUAOH, AnAOH and AnGOH (where n is about 10). Patterns from samples subjected to exhaustive digestion with ribonucleases T1 plus A, or with each separately, confirmed these inferences, and strikingly demonstrated the existence of oligoadenylated families of 3'-terminal sequences. Under the assumption that the oligoadenylate was added posttranscriptionally, these results indicated that the 3'-terminal transcribed moieties consist of variants of YAGGUUOH. Counting from the last U, we inferred that many such sequences end at U1 and G4, while smaller numbers end at G3 and A5; and that major sites of oligoadenylation occur at U1 and G4, and a minor site occurs at A5. This novel combination of imprecise termination of transcription or "sizing" of transcripts, and variable addition of adenylate residues, is discussed with regard to the mechanism of expression of the mammalian mitochondrial ribosomal RNA genes.