The crystal structure of the ribosome bound to EF-Tu and aminoacyl-tRNA.

The ribosome selects a correct transfer RNA (tRNA) for each amino acid added to the polypeptide chain, as directed by messenger RNA. Aminoacyl-tRNA is delivered to the ribosome by elongation factor Tu (EF-Tu), which hydrolyzes guanosine triphosphate (GTP) and releases tRNA in response to codon recognition. The signaling pathway that leads to GTP hydrolysis upon codon recognition is critical to accurate decoding. Here we present the crystal structure of the ribosome complexed with EF-Tu and aminoacyl-tRNA, refined to 3.6 angstrom resolution. The structure reveals details of the tRNA distortion that allows aminoacyl-tRNA to interact simultaneously with the decoding center of the 30S subunit and EF-Tu at the factor binding site. A series of conformational changes in EF-Tu and aminoacyl-tRNA suggests a communication pathway between the decoding center and the guanosine triphosphatase center of EF-Tu.