Ribosome recycling factor (RRF) together with elongation factor G (EF-G) catalyses recycling of prokaryotic ribosomes after a completed round of protein synthesis. At this stage, the ribosome is bound to an mRNA stop codon and presumably has an empty A site. The deacylated tRNA, from which the nascent peptide has been detached, sits in the P site. The action of RRF and EF-G is to catalyse disassembly of this complex into 70S ribosome, mRNA, and tRNA.

The structure of RRF from Thermotoga maritima was solved [1] using data collected at beamline BM14. Three wavelength MAD data to 2.9 Å was collected at 100 K using selenomethionine substituted crystals.

RRF consists of an elongated three-helix bundle domain and a ß//ß sandwich (Figure 5). Together they superimpose almost perfectly with a tRNA molecule. This mimicry suggests that RRF binds to the ribosome similarly to a tRNA molecule.

Figure 5
Fig. 5: RRF is an L-shaped molecule with dimensions 70 x 47 x 20 Å. 

Principal Publication and Authors
[1] M. Selmer (a), S. Al-Karadaghi (a), G. Hirokawa (b), A. Kaji (b) and A. Liljas (a), Science, 286, 2349-2352 (1999).
(a) Molecular Biophysics, Lund University (Sweden)
(b) University of Pennsylvania, Philadelphia (USA)