[Comparative analysis of affinity modification of several aminoacyl-tRNA synthetases with gamma-(p-azidoanilide)-ATP].

The inhibitory action of gamma-(p-azidoanilide)-ATP on the reactions of tRNA aminoacylation catalysed by several aminoacyl-tRNA synthetases was investigated. This compound was shown to be a competitive inhibitor with respect to ATP in the case of arginyl-, valyl-, isoleucyl-, leucyl-, threonyl-, phenylalanyl-tRNA synthetases of E. coli MRE-600 and tryptophanyl-tRNA synthetase of beef pancreas. The Ki value of this analog changes from 3 x 10(-5) up to 4 x 10(-3) M depending on the enzyme specificity. In the case of methionyland lysyl-tRNA synthetases from E. coli the non-competitive and mixed inhibition accordingly was observed. The activity of isoleucyl-, valyl-, leucyl-, threonyl-, phenyl-alanyl- and tryptophanyl-tRNA synthetases in the reaction of tRNA aminoacylation is decreased as a result of UV-irradiation of the enzymes in the presence of gamma-(p-azidoanilide)-ATP. ATP and aminoacids protect these enzymes against irreversible inactivation. These results confirm the affinity labelling of the substrate binding sites of these enzymes. However, the appreciable inactivation of enzymes with UV-irradiation in the presence of gamma-(p-azidoanilide)-ATP was not detected in the cases of hystidyl-, lysyl-, methionyl-, seryl-, tyrosyl- and phenylalanyl-tRNA synthetases of E. coli MRE-600. The data obtained enable one to suggest the difference in the structure of the amino acid activating sites of different aminoacyl-tRNA synthetases.