Molecular weight distribution of proteins in rabbit reticulocyte ribosomal subunits

Abstract

The molecular weight distribution of ribosomal proteins in subunits of rabbit reticulocyte ribosomes was studied by electrophoresis in polyacrylamide gels containing sodium dodecyl sulphate. The relative migration rates of the different proteins lead to a description of their molecular weights, while the intensity of staining provides a measure of the relative amounts of protein. Subunits active in protein synthesis derived from ribosomes by salt-dissociation appear to contain 40 to 60 proteins in the molecular weight range 8000 to 57,000 (large subunit) and 30 to 40 proteins in the molecular weight range 6000 to 39,000 (small subunit). The proteins from salt-dissociated ribosomes display the same electrophoretic patterns as those of natural ribosomal subunits. The proteins from inactive subunits produced when ribosomes dissociate in EDTA, however, indicate the apparent transfer of a protein from the large subunit to the small subunit upon dissociation.