Interference of ligands on the phenylalanyl-tRNA synthetase from yeast.
The present paper reports a study of the mutual interactions between the substrates, the intermediate, and the products of the aminoacylation reaction, when bound to the phenylalanyl-tRNA synthetase from yeast. The following conclusions can be drawn. a) tRNAPhe displaces Phe-tRNAPhe from the synthetase by lowering the affinity of the enzyme for the aminoacylated tRNA. b) Phe-tRNAPhe and Phe-AMP compete for the catalytically active site of the enzyme. c) Chemically synthesized Phe-AMP, when added to the synthetase, primarily forms a low-affinity complex with the enzyme. The transformation of this complex into the high-affinity catalytic complex is a very slow process. These findings confirm a previous study, based on steady-state kinetics. A schematic representation of the aminoacylation process is given. It summarizes the present and previous results and illustrates a rather complex 'flip-flop' mechanism.
D000604:Amino Acyl-tRNA Synthetases / Q000037:antagonists & inhibitors*; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D008024:Ligands / Q000494:pharmacology*; D010652:Phenylalanine-tRNA Ligase / Q000037:antagonists & inhibitors*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
D008024:Ligands; D000604:Amino Acyl-tRNA Synthetases; D010652:Phenylalanine-tRNA Ligase