Ribosome-membrane interactions: characterization of ribosomal proteins from loose and tight bound ribosomes.

Membrane-bound ribosomes were isolated from a post-mitochondrial supernatant fraction of mouse liver homogenate by sedimentation in a sucrose density gradient, Loose ribosomes were released from the membrane fragments with 0.5 M KCl, while tight bound ribosomes were not released. After purification of the loose and tight ribosomes subclasses, ribosomal subunit proteins were isolated and compared by two-dimensional polyacrylamide gel electrophoresis. No differences in the ribosomal protein composition was detected.