Ribosome-Recycling Factor: an Essential Factor for Protein Synthesis

This chapter reviews key experimental findings about ribosome-recycling factor (RRF) up to May 1999. Escherichia coli RRF is a basic protein with a molecular mass of approximately 20 kDa consisting of 185 amino acids. The molar amount of RRF in a cell is approximately one-half the total molar amount of ribosome, and approximately 30% of total cellular RRF is bound to ribosomes. The ribosome has to be at the termination codon for the release because removal of Asn from the reaction mixture significantly reduced the RRF reaction. In the puromycin-treated polyribosome, each ribosome presumably has an empty A site and bound deacylated tRNA at the P site, a structure similar to that of the posttermination complex. The RRF reaction is dependent on GTP and either elongation factor G (EF-G) or release factor 3 (RF3) in a 1:1 stoichiometric relationship. The important difference between the posttermination complex and the elongation complex is that the former has deacylated tRNA instead of peptidyl-tRNA. This difference leads to disassembly on the one hand and to translocation on the other. In fact, even in the presence of peptidyl-tRNA, RRF may accidentally disassemble the elongating complex. The recycling time of translation was shortened significantly by the addition of RRF and RF3. The bactericidal and bacteriostatic effects of inhibition of RRF suggest that RRF may be an ideal target for antibacterial agents.