Reconstitution of the active rat liver 60 S ribosomal subunit from different preparations of core particles and split proteins

Proteins extracted from the 60 S rat liver ribosomal subunit with 50% ethanol/0.5 M K Cl produced only a partial reactivation of the corresponding core particles. In contrast, the same split proteins were able to reactivate the core particles prepared with dimethyl-maleic anhydride (DMMA) to the same level as that observed using the DMMA-split proteins, i.e. 60-80% of the control according to the catalytic activities tested. Comparative analysis of the two split protein fractions showed only four common proteins: P1-P2, which alone restored part of the activities, especially the EF-2-dependent GTPase one, and L10a, L12, which must be responsible for the additional reactivation. The poor ability of the ethanol/KCl core particles to be reactivated was shown to be probably related to a conformational alteration which destabilized the 5 S RNA-protein complex. Proteins present in the ethanol/KCl wash of Saccharomyces cerevisiae 60 S subunits were found to be partly active in subunit reconstitution using rat liver DMMA core particles.