Studies on the aminoacylation of valine- and alanine-specific transfer RNA of Escherichia coli by aminoacyl transfer RNA synthetases from Neurospora crassa and E. coli

The interaction of valine- and alanine-specific tRNA (tRNA Val and tRNA Ala) from Escherichia coli with phenylalanyl-tRNA synthetase from Neurospora crassa results in the production of phe-tRNA Val and phe-tRNA Ala. In this case of misrecognition the amount of aminoacyl-tRNA produced is 0.3–0.5 of the amount expected. The various isoaccepting forms of tRNA Val and tRNA Ala were obtained by reversed phase chromatography and were all active in accepting phenylalanine from the N. crassa enzyme. The isoaccepting forms of tRNA Ala differed in the inhibition of the N. crassa enzyme by salt. Comparing tRNA ( E. coli) and tRNA ( N. crassa) shows that the reaction of the phenylalanyl-tRNA synthetase ( N. crassa) with the former is inhibited by NaCl and with the latter is stimulated by NaCl. We conclude that the limited amount of aminoacylation of tRNA Val and tRNA Ala by phenylalanine tRNA synthetase ( N. crassa) is not due to a specificity that restricts the enzyme to certain isoaccepting forms of the tRNA's. The stimulation or inhibition of the N. crassa enzyme by NaCl depending on which tRNA is the substrate may indicate that a different reaction mechanism is followed for the two tRNA's.