Physical Reconstitution of 23 S RNA – 50 S Protein Complexes from Escherichia coli

The formation of ribosomal complexes in a system containing 50 S ribosomal proteins and ribosomal RNA (5, 16, and 23 S RNA's) is reported. Binding of 50 S proteins to 23 S RNA resulted in reconstituted particles that sedimented at 28, 32, 43, and 48 S. The process was highly influenced by temperature and indicated at least three temperature-dependent steps. The 28 S particle contained 14–20 proteins and formation of the largest particles was accompanied by the sequential binding of at least six to seven more proteins. The formation of 28 and 32 S complexes was independent of 5 and 16 S RNA's, as well as 30 S proteins or 30 S subunits. The failure to form functional 50 S subunits is discussed.