[Modification of one tRNA recognition site of phenylalanyl-tRNA synthetase from E. coli MRE-600 with N-chlorambucilyl-phenylalanyl-tRNA].

Affinity labelling of phenylalanyl-tRNA synthetase from E. coli MRE-600 with N-chlorambucilyl-phenylalanyl-tRNA results in a binding of 1 mole of the reagent per 1 mole of the enzyme. Exhaustive alkylation of phenylalanyl-tRNA synthetase completely blocks the aminoacylation and partially inhibits the reaction of ATP--[32P]pyrophosphate exchange. Removal of the tRNA moiety of the reagent by hydrolysis of the ester bond N-chlorambucilyl-phenylalanine and terminal adenosine does not result in a restoration of ATP--[32P]pyrophosphate exchange and aminoacylation activity. The latter result may testify a chemical modification of amino acid residues essential for enzymatic activity. Possibility of blocking one of the two tRNA binding sites is discussed.