Inhibition by Elongation Factor EF G of Aminoacyl-tRNA Binding to Ribosomes

Elongation factor G (EF G), bound to ribosomes either with GMPPCP or with fusidic acid and GDP, inhibits elongation factor Tu (EF Tu)-dependent binding of Phe-tRNA on the ribosome-poly(U) complex and binding of Ala-tRNA on the initiation complex formed with RNA from bacteriophage R17; GTP hydrolysis associated with Phe-tRNA binding is also inhibited. Moreover, nonenzymic binding of Phe-tRNA at high Mg⁺⁺ concentration is completely blocked by EF G. Thus, EF G appears to bind at a site that overlaps or interacts with the ribosomal A-site.