Identification of a Wheat Germ Ribosome Dissociation Factor Distinct from Initiation

SUMMARY A ribosome dissociation factor(s) has been partially purified from extracts of wheat germ. This factor can be detected by its ability to prevent the reassociation of ribosomal subunits when the magnesium concentration is raised from 1 mM to 5 mM. The majority of the dissociation factor activity is found in the postribosomal supernatant of the cell and can be precipitated between 0 and 40% ammonium sulfate. Chromatography of this material on DEAE-cellulose yields a fraction which contains both the dissociation factor activity and initiation factor eIF-3. However, the majority of the dissociation factor activity can be readily separated from eIF-3 by chromatography on phosphocellulose. The dissociation factor appears to be distinct from any of the other known wheat germ initiation factors.