title: Kinetic studies on the interactions of Escherichia coli K12 elongation factor Tu with GDP and elongation factor Ts.
abstract: The kinetic parameters describing the dissociation of GDP from the elongation factor Tu (EF-Tu) . GDP complex in the absence and presence of elongation factor Ts (EF-Ts) have been characterized using an equilibrium isotope exchange technique. The rate constant for dissociation of GDP from EF-tu was found to be 1.7 x 10(-3) s-1. Since this dissociation rate is greatly enhanced by EF-Ts, it follows that the dissociation of GDP in the presence of EF-Ts proceeds via the formation of a ternary EF-Tu . GDP . EF-Ts complex as represented below: EF-Tu . GDP + EF-Ts in equilibrium EF-Tu . GDP . EF-Ts in equilibrium EF-Tu . EF-Ts + GDP. Analysis of the exchange kinetics according to this reaction scheme yields a rate constant for the dissociation of GDP from the ternary complex of greater than or equal to 1270 s-1. The equilibrium association constants for GDP and EF-Ts to form the ternary complex was found to be 6.4 x 10(4) M-1 and 1.8 x 10(5) M-1, respectively. These results demonstrate that the dissociation of GDP from EF-Tu in the presence of EF-Ts is not the rate-limiting process in protein synthesis.
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D005374:Filtration / Q000295:instrumentation; D006150:Guanine Nucleotides / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D007700:Kinetics; D008433:Mathematics; D010444:Peptide Elongation Factor Tu; D010445:Peptide Elongation Factors / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D006150:Guanine Nucleotides; D010445:Peptide Elongation Factors; C023512:elongation factor Ts; D006153:Guanosine Diphosphate; D010444:Peptide Elongation Factor Tu