Amino‐acylation du tRNA₁Val de Escherichia coli par la phéenylalanyl‐tRNA synthétase de levure

Comparison of the known primary structures of several tRNAs reveals striking similarities between the nucleotide sequences of yeast tRNA phe and Escherichia coli tRNA 1 Val . On the assumption that such structural analogy might lead to aminoacylation of both tRNAs by each of the corresponding aminoacyl‐tRNA synthetases, a detailed study of this system was undertaken. The results indicate that under optimal conditions, E. coli tRNA 1 Val can be completely aminoacylated by yeast phenylalanyl‐tRNA synthetase, while the reciprocal ( i.e. valyl‐tRNA Phe (yeast) formation by E. coli valyl‐tRNA synthetase) could not be demonstrated under any of a variety of conditions tested. Conditions for Phe‐tRNA 1 Val ( E. coli ) formation by yeast phenylalanyl‐tRNA synthetase differ radically from those leading to aminoacylation of tRNA in homologous systems. In particular, the final yield of aminoacyl‐tRNA varies with enzyme concentration and is markedly affected by the nature of the buffer and the pH, as well as by the presence of monovalent cations and organic solvents such as ethanol and dimethyl sulfoxide. Similar observations have already been reported in the study of the aminoacylation of tRNA in several heterologous systems. The results are discussed in relation to the structure of the two tRNAs.