Reversible modification of 50S ribosomal subunits with dimethylmaleic anhydride: protein-deficient particles.

The reversible modification of protein amino groups with dimethylmaleic anhydride, which had already been used to dissociate proteins from the 70S ribosomes of Escherichia coli (Pintor-Toro, J. A., et al. (1979) Biochemistry 18, 3219) was applied to the preparation of protein-deficient particles from the 50S subunits. Three successive cycles of treatment with dimethylmaleic anhydride, separation of dissociated proteins and regeneration of the modified amino groups produce partially inactivated ribosomal 'cores' lacking proteins L7, L11 and L12, and having very small amounts of L1, L6 and L10. Incubation of these 'cores' with the corresponding split proteins is accompanied by complete reactivation of the polypeptide synthesizing activity as compared with control 50S subunits.