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Dissociation of eukaryotic ribosomes by purified initiation factor EIF-3

1973; Elsevier BV; Volume: 54; Issue: 1 Linguagem: Inglês

10.1016/0006-291x(73)90915-7

1090-2104

Kazuyasu Nakaya, Rajinder Singh Ranu, Ira G. Wool,

RNA Interference and Gene Delivery

Purified eukaryotic initiation factor, EIF-3, prepared from ascites cells dissociated rat liver 80S ribosomes into subunits. Ribosomes bearing endogenous mRNA and nascent peptide were not dissociated by EIF-3. When 80S ribosomes reconstituted from subunits were used as substrate the reaction had the following characteristics: Dissociation was rapid--the reaction being completed within 2 min at 30°. The extent of dissociation was directly proportional to the amount of EIF-3; with 21 μg of EIF-3 about 70% (or 10.5 μg) of the 80S monomers were dissociated. The dissociation of 80S monomers by EIF-3 decreased with increasing concentrations of magnesium. The reaction was not catalytic: 28 moles of EIF-3 were required to dissociate 1 mole of 80S ribosomes. The characteristic of the dissociation reaction promoted by EIF-3 and by E. coli initiation factor IF-3 are remarkably similar. The dissociation reaction provides a practical assay for EIF-3 independent of complimentation of other initiating factors.