RESUMEN
Fluorescence studies with organelle transfer RNAs separated from their cytoplasmic counterparts revealed that phenylalanine tRNA from Euglena chloroplasts or Neurospora mitochondria does not contain a fluorescent "base Y." In contrast, cytoplasmic phenylalanine tRNA from Euglena and cytoplasmic tRNA from Neurospora were found to contain fluorescent bases. The fluorescence-emission spectra of Neurospora cytoplasmic tRNAs and those of the related ascomycete Saccharomyces cerevisiue were observed to be quite different. The results support the generalization that eukaryotic tRNAs contain a fluorescent base, but indicate that their respective organelle tRNAs do not. They also indicate a striking parallelism between organelle and prokaryotic tRNAs.
Asunto(s)
Cloroplastos/análisis , Citoplasma/análisis , Euglena gracilis/citología , Mitocondrias/análisis , Neurospora/citología , ARN de Transferencia/análisis , Acilación , Cromatografía , Cromatografía DEAE-Celulosa , Euglena gracilis/análisis , Fluorescencia , Neurospora crassa/citología , Fenilalanina/biosíntesis , Fenilalanina/metabolismo , Fotosíntesis , Saccharomyces cerevisiae/citología , TritioRESUMEN
Light-grown, wild type Euglena gracilis contains two aminoacyl-tRNA synthetases for both phenylalanine and isoleucine. Only one of the two synthetases for each amino acid is found in isolated chloroplasts, as are the light-induced phenylalanine and isoleucine tRNAs. In each case the light-induced chloroplast tRNAs can only be acylated by the chloroplast synthetases. The chloroplast isoleucyl-tRNA synthetase is light-inducible and cannot be detected in dark-grown cells or in cells of the bleached mutant W(3)BUL. The presence of the chloroplast phenylalanyl-tRNA synthetase in W(3)BUL, which contains no chloroplast DNA or structure, indicates that this chloroplast enzyme is synthesized in the cytoplasm and is coded by nuclear genes.
Asunto(s)
Cloroplastos/enzimología , Inducción Enzimática , ARN Nucleotidiltransferasas/análisis , ARN de Transferencia/análisis , Aminoácidos , Cromatografía DEAE-Celulosa , Euglena , Código Genético , LuzRESUMEN
Exposure of dark-grown, wild-type Euglena gracilis to light induces the formation of at least three new chromatographic species of tRNA. Parallel studies with a bleached mutant (W(3)BUL) of Euglena demonstrate that the induction of these new tRNA species is dependent upon the cell's ability to form chloroplasts and rule out the possibility that the new species arise from an effect of light on the tRNA's per se.
