Resistance of Active Yeast Ribosomes to Dissociation by KCl

Monoribosomes deficient in messenger RNA which accumulate in a temperature-sensitive yeast mutant at the restrictive temperature were compared for their dissociability in 0.8 m KCl with polyribosomes and with monoribosomes derived from polyribosomes by ribonuclease treatment. It was found that ribosomes from yeast are dissociated into subunits in 0.8 m KCl only if they lack attached messenger RNA. Ribosomes lacking messenger RNA can be converted to a KCl-stable form by incubation in vitro with transfer RNA, polyuridylic acid, and supernatant.