Factor-promoted dissociation of free ribosomes in a rabbit reticulocyte lysate system: inhibition and requirement for an energy source.

A factor that promoted the dissociation of ribosomes into ribosomal subunits in a complete globin-synthesizing system was isolated from rabbit reticulocyte ribosomes. The factor stimulated both globin synthesis and the association of the small ribosomal subunit with polyribosomes. The dissociation of free ribosomes by the factor could be followed as an independent reaction in the presence of a high concentration of cycloheximide, which inhibited translation and the resulting accumulation of runoff subunits. This reaction required an energy source and was inhibited by P-(5'-guanylyl)-methylenebisphosphonate. These data suggest that energy generated by hydrolysis of GTP may be a requirement for the dissociation reaction. Aurintricarboxylic acid inhibited the factor-mediated dissociation of free ribosomes but not the factor-mediated preservation of subunits formed on peptide-chain termination.