Crystal structure of the hybrid state of ribosome in complex with the guanosine triphosphatase release factor 3.

Protein release factor 3 (RF3), a guanosine triphosphatase, binds to ribosome after release of the nascent peptide and promotes dissociation of the class I release factors during the termination of protein synthesis. Here we present the crystal structure of the 70S ribosome with RF3 in the presence of a nonhydrolyzable GTP analogue, guanosine 5'-β,γ-methylenetriphosphate (GDPCP), refined to 3.8 Å resolution. The structure shows that the subunits of the ribosome are rotated relative to each other compared to the canonical state, resulting in a P/E hybrid state for the transfer RNA. The substantial conformational rearrangements in the complex are described and suggest how RF3, by stabilizing the hybrid state of the ribosome, facilitates the dissociation of class I release factors.