title: ATP-induced activation of the aminoacylation of tRNA by the isoleucyl-tRNA synthetase from Escherichia coli.
abstract: The rate of aminoacylation of tRNA catalyzed by the isoleucyl-tRNA synthetase form Escherichia coli has been measured. A steady-state kinetic analysis of the rate as a function of the concentration of ATP gave nonlinear Hanes plots. ATP behaves as an activator of the reaction. The activation is observed at a low magnesium ion concentration and in the presence of spermidine. The presence of inorganic pyrophosphate or AMP enhances the activation. The results are consistent with a mechanism in which the binding of a second molecule of ATP increases the rate of dissociation of Ile-tRNA from the enzyme.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D001665:Binding Sites; D055598:Chemical Phenomena; D002621:Chemistry; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D007533:Isoleucine-tRNA Ligase / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008433:Mathematics; D012343:RNA, Transfer / Q000378:metabolism*; D013095:Spermidine / Q000378:metabolism
chemical_list: D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases; D007533:Isoleucine-tRNA Ligase; D008274:Magnesium; D013095:Spermidine