Comparison of the Hydrolysis Patterns of Several tRNAs by Cobra Venom Ribonuclease in Different Steps of the Aminoacylation Reaction

Open Access
Publisher Website
Google Scholar
Abstract
The hydrolysis of several tRNA by an endonuclease extracted from the venom of Naja oxiana and specific for doubled-stranded, or at least highly ordered, regions was studied under various experimental conditions. The hydrolysis patterns of brewer''s yeast tRNAPhe, tRNAVal and tRNAAsp in the isolated state are similar, most of the cuts occurring in the anticodon and acceptor stems. Ionic conditions are able to modify the hydrolysis pattern. The origin of these modifications is discussed. The protection against RNase action, afforded to tRNAPhe, tRNAVal and tRNAAsp by the cognate aminoacyl-tRNA synthetase, is analyzed. In all cases the anticodon stem is protected. The 3''-terminal region does not seem to be tightly engaged in the complex with the aminoacyl-tRNA synthetase. These results are discussed in the light of information on contact areas previously obtained by UV cross-linking techniques. The effects of the small ligands (ATP and amino acid) on the protection afforded to the tRNA by the cognate synthetase were studied. In the valine and aspartic acid systems, ATP induced a modification of the tRNA-enzyme complex leading to differences in the hydrolysis pattern of the 3''-accepting region. The effects of aminoacylation on the cleavage of tRNAPhe, tRNAVal and tRNAAsp were also studied. Whereas no modification of the cleavage map was observed in the aspartic system, aminoacylation resulted in slight but significant modifications of the hydrolysis pattern for tRNAPhe and tRNAVal in the 3''-terminal region.