CRYSTAL-STRUCTURE OF THE TERNARY COMPLEX OF PHE-TRNA(PHE), EF-TU, ANDA GTP ANALOG

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 determin ed by x-ray crystallography at 2.7 angstrom resolution. The ternary co mplex participates in placing the amino acids in their correct order w hen messenger RNA is translated into a protein sequence on the ribosom e. The EF-Tu-GDPNP component binds to one side of the acceptor helix o f Phe-tRNA(Phe) involving all three domains of EF-Tu. Binding sites fo r the phenylalanylated CCA end and the phosphorylated 5' end are locat ed at domain interfaces, whereas the T stem interacts with the surface of the beta-barrel domain 3. The binding involves many conserved resi dues 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 apparat us.