Stoichiometry of the EF‐Tu · GTP complex with aminoacyl‐tRNA: ternary of quinternary?

The stoichiometry of the complex formed between the Escherichia coli polypeptide elongation factor EF-Tu, GTP and valyl-tRNA(val) has been determined by non-enzymatic deacylation studies on mixtures of the components at well-defined concentrations. A titration end-point was found corresponding to a 1:1 complex of EF-Tu.GTP with the aminoacylated-tRNA i.e. formation of a ternary complex. The result conforms to the classical model of the elongation step and not to the revolutionary proposition of the formation of a 2:2:1 complex; quinternary complex (EF-Tu.GTP)2.aa-RNA.