Protein biosynthesis: structural studies of the elongation cycle

The elongation cycle of protein synthesis on ribosomes is catalyzed by the elongation factors EF-Tu and EF-G. A thorough crystallographic analysis of the structures of the different functional states of EF-Tu has been made. Furthermore, the structure of EF-G:GDP is the form of EF-G that dissociates from the ribosome. Since it mimics the structure of the ternary complex of EF-Tu:GTP with aminoacyl-tRNA, which subsequently binds to the ribosome, EF-G:GDP leaves an imprint on the ribosome for the ternary complex. In addition, electron cryomicroscopy studies of ribosomes with tRNA as well as the ternary complex bound are beginning to give a solid structural basis for the functional description of elongation.