Activity of a transfer RNA modifying enzyme during the development of Drosophila and its relationship to the su(s) locus

The Chromatographie elution profiles of radioactively labeled asparaginyl, aspartyl, histidyl and tyrosyl-tRNA's from different developmental stages of Drosophila melanogaster have been examined. The relative proportions of certain chromatographically distinct forms of these four tRNA's are altered in a similar way during the life cycle of wild-type flies. These four tRNA's show a further quantitative change in flies of the genotype su(s)2v;bw. Two-dimensional thin-layer chromatograms of pancreatic RNase digests of the two major tRNAAsp Chromatographie forms revealed almost identical patterns. Two-dimensional thin-layer chromatograms of piperidine hydrolysates of these tRNA's revealed that one contained a nucleotide similar to Qp, an unidentified nucleotide occurring in Escherichia coli tRNA. It was concluded that these Chromatographie forms are homogeneic††We propose the term homogeneic to describe tRNA's having the same sequence and presumably being products of the same gene, but which are cbromatographically distinct because of different degrees of post-transcriptional modification., the difference between them being the extent of the modification of one nucleotide. The su(s)2v;bw mutant appears to be altered in some aspect of this modification process.