Ribosome recycling factor disassembles the post-termination ribosomal complex independent of the ribosomal translocase activity of elongation factor G

Ribosome recycling factor (RRF) disassembles post-termination ribosomal complexes in concert with elongation factor EF-G freeing the ribosome for a new round of polypeptide synthesis. How RRF interacts with EF-G and disassembles post-termination ribosomes is unknown. RRF is structurally similar to tRNA and is therefore thought to bind to the ribosomal A site and be translocated by EF-G during ribosome disassembly as a mimic of tRNA. However, EF-G variants that remain active in GTP hydrolysis but are defective in tRNA translocation fully activate RRF function in vivo and in vitro. Furthermore, RRF and the GTP form of EF-G do not co-occupy the terminating ribosome in vitro; RRF is ejected by EF-G from the preformed complex. These findings suggest that RRF is not a functional mimic of tRNA and disassembles the post-termination ribosomal complex independently of the translocation activity of EF-G.