A consideration of Euglena gracilis W3BUL as a cytoplasmic control for the wild-type phenylalanyl-tRNA synthetase...

The studies described indicate that the UV bleached mutant, Euglena gracilis W3BUL does not serve as a suitable cytoplasmic control for the phenylalanyl-tRNA synthetase system. Chromatography of wild-type E. gracilis on Sephadex G100 revealed three peaks of activity identified as the chloroplastic, cytoplasmic and mitochondrial enzymes. The chloroplastic activity was greater in log than in stationary phase cells and was the only activity recovered from purified chloroplasts. Cell-free extracts of the achloroplstic mutant, E. gracilis W3BUL, contained wild-type levels of the cytoplasmic and mitochondrial phenylalanyl-tRNA synthetases. However, no chloroplastic synthetase was detected in the mutant extracts. Anomalies in the aminoacylation behavior of the W3BUL system were observed which suggest the possibility of a mutation affecting non-chloroplastic tRNAs in this UV-induced mutant. These anomalies significantly reduce the ability of the E. gracilis W3BUL mutant to serve as a cytoplasmic control in the phenylalanyl-tRNA synthetase system.