[Role of the lysine residues in the phenylalanyl-tRNA synthetase substrates interaction].

The effect of 2,4-pentandione on the activity of phenylalanyl-tRNA synthetase (Phe-RSase) from E. coli MRE-600 was investigated. It was shown that modification of Phe-RSase with 2,4-pentandione leads to decrease of the aminoacylation rate without an influence on the ATP--[32P]pyrophosphate exchange reaction rate. tRNAPhe protects the enzyme against inactivation. Neither L-Phe and ATP nor the analog fo aminoacyladenylate protects the enzyme against inactivation. There are no changes in Km for amino acid and ATP in the aminoacylation reaction after modification while Km for tRNAPhe decreases three times. The dissociation constant of Phe-RSase: [14C]Phe-tRNA complex increases 4--8 times after modification. It is assumed that there are some lysine residues in Phe-RSase essential for the Phe-RSase-tRNA interaction.