Crystal Structure of the Ternary Complex of Phe-tRNA Phe , EF-Tu, and a GTP Analog

Abstract

The structure of the ternary complex consisting of yeast phenylalanyl-transfer RNA (Phe-tRNA^Phe), Thermus aquaticus elongation factor Tu (EF-Tu), and the guanosine triphosphate (GTP) analog GDPNP was determined by x-ray crystallography at 2.7 angstrom resolution. The ternary complex participates in placing the amino acids in their correct order when messenger RNA is translated into a protein sequence on the ribosome. The EF-Tu-GDPNP component binds to one side of the acceptor helix of Phe-tRNA^Phe involving all three domains of EF-Tu. Binding sites for the phenylalanylated CCA end and the phosphorylated 5′ end are located at domain interfaces, whereas the T stem interacts with the surface of the β-barrel domain 3. The binding involves many conserved residues in EF-Tu. The overall shape of the ternary complex is similar to that of the translocation factor, EF-G-GDP, and this suggests a novel mechanism involving “molecular mimicry” in the translational apparatus.