ARGINYL-tRNA SYNTHETASE FROM Escherichia coli AFFINITY LABELING WITH 3’-OXIDIZED tRNAArg

The covalent modification of E. coli arginyl-tRNA synthetase by the 2’,3’-dialdehydederivative of tRNAArg (tRNAoxArg) resulted in the complete inactivation of the ATP-PPi ex-change and aminoacylation activities of the enzyme. Sodium dodecyl sulfate polyacrylamide gelelectrophoresis of the ArgRS-tRNAoxArg covalent complexes indicated that two bands simulta-neously appeared on the gel parallel with inactivation corresponding to different higher mo-lecular weights. This result was different from that of the other aminoacyl-tRNA synthetaselabeling systems as previously reported. Upon the ribonuclease treatment of the modifiedArgRS, less than 15% of both the initial ATP-PPi exchange and aminocylation activities wererecovered. During the whole process of labeling and RNase treatment, the two activities ofthe enzyme were closely associated.