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

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Abstract
Proteins extracted from the 60 S rat liver ribosomal subunit with 50% ethanol/0.5 M KCl 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.