Elongation factors EF Tu and EF G interact at related sites on ribosomes.

The binding of elongation factor EF G to ribosomes inhibits the subsequent reaction of the ribosomes with the ternary complex aminoacyl-tRNA.EF Tu.GTP. Both the hydrolysis of GTP and the binding of aminoacyl-tRNA to ribosomes are nearly abolished by the previous binding of factor EF G to ribosomes in the presence of either fusidic acid plus either GTP or a nonhydrolyzable analog of GTP. The results suggest that each elongation factor binds to the same region on the ribosome. The GTPase activities of both factors EF G and EF Tu may be activated by interaction at the same ribosomal site, as has been previously suggested by others.