Interaction of Elongation Factor Tu with the Aminoacyl Transfer Ribonucleic Acid Dimer Phe-tRNA-Glu-tRNA

The effect of EF-Tu·GTP on the codon-anticodon interaction of AA-tRNA was studied by using as a model system the interaction of AA-tRNAs with complementary anticodons, namely, dimerization between yeast or Escherichia coli Phe-tRNA^(Phe) (anticodon GmAA) and E. coli GlutRNA^(Giu) (anticodon _s^2UUC) or nonacylated tRNA^(Giu) in the presence or absence of EF-Tu·GTP. The present data indicate that the ternary complexes Phe-tRNA-EF-Tu·GTP and Glu-tRNA-EF-Tu·GTP can form dimers with a binding constant of (0.9 ± 0.2) X 10^6 M^(-1), which is identical in magnitude with that of the dimer of the nonacylated tRN As tRNA^(Phe)-tRNA^(Giu) and also with that of the complex PhetRNA-EF-Tu·GTP with nonacylated tRNA^(Giu). These results show that the anticodon region is not affected by complexation with EF-Tu·GTP; however, this conclusion does not preclude the possibility of structural changes in the anticodon loop that have no effect in energetic terms. In addition, this model codon-anticodon interaction does not stimulate hydrolysis of the GTP bound in the ternary complex