Ribosomal subunits were prepared from rat liver and skeletal muscle after incubation with puromycin and treatment at low concentrations of Mg2+. After isolation the resulting subunits could be recombined and the particles effected the synthesis of polyphenylalanine in the presence of polyuridylic acid. Hybrid particles formed from subunits of liver and muscle respectively were also active. The homogeneity of the isolated subunits was checked by polyacrylamide-gel–agarose electrophoresis. The method is shown to be a reliable and comparatively simple way of preparing active ribosomal subunits from skeletal muscle.
