Structure of Phenylalanyl-tRNA synthetase complexed with cognate tRNA
The aaRSs promote a close control over two-step aminoacylation reaction and thus establishing linkage between cognate amino acid and three nucleotides of the tRNA anticodon(s). The aaRSs must bind and recognize three ligands: amino acid, ATP and tRNA. At the first step aaRS activates amino acid forming an aminoacyl-adenylate intermediate. At the second step the amino acid moiety is transferred to the 3'-terminal ribose of tRNA. Although, aaRSs catalyze the same two-step reaction idiosyncrasy of each system imply peculiarity of stereochemical aspects of individual aminoacylation reactions and fine stepwise (ordered) adjustment of all the reactants and their intermediates in the active site.