Small-angle neutron scattering study of the ternary complex formed between bacterial elongation factor Tu, guanosine...

The formation of the ternary complex between bacterial elongation factor Tu, GTP, and valyl-tRNAVal has been studied by small-angle neutron scattering. Titrations of the protein with amino-acyl-tRNA solutions in both H2O and 70% D2O confirm the expected stoichiometry. The molecular weight obtained for the protein alone is significantly higher than expected and can be explained by postulating a monomer-dimer equilibrium. The titration data are then internally consistent with a dissociation of the dimer on ternary complex formation. The radius of gyration for the ternary complex and the calculation of the separation of the centers of mass of the protein and tRNA components suggest a compact model for the ternary complex.