Studies on tRNA and aminoacyl-tRNA synthetases during the development of Rana pipiens

Abstract

Amphibian embryos at different developmental stages have been studied with respect to their aminoacyl-tRNA synthetases and tRNA. Synthetase preparations from each embryonic stage were active in aminoacylation of tRNA and showed properties similar to synthetases from other sources as judged by the ATP-PP i exchange and hydroxamate formation reactions. Transfer-RNA was quantitated in two ways: one by the total amount of A 260 material in the 4 S fraction of preparations from different developmental stages, and the other by measuring the amino acid acceptor activity of these same preparations aminoacylated with stage 25 synthetases. The two methods gave very different values for tRNA from early embryonic stages. Only a small part of the difference could be accounted for by the amount of inactive tRNA from early embryos. Preliminary experiments indicate that most of the difference noted was due to changes in the tRNA and synthetase pools during embryogenesis. Furthermore, it is suggested that two major groups of these macromolecules are present: one group appears predominate between ovulation and gastrulation, and the other gains dominance during subsequent development.