Distribution of Protein Assembly Sites along the 23‐S Ribosomal RNA of Escherichia coli

The protein composition of the 13‐S and 18‐S ribonucleoproteins isolated after mild ribonuclease digestion of Escherichia coli ribosomal 50‐S subunits were examined and those proteins specifically assembled were identified. Many proteins were unspecifically hound but some could subsequently be reassembled specifically by high‐salt treatment and they were identified. Three RNA compooents were isolated from these ribonucleoproteins, namely 13‐S RNA from the 5′ end and 11‐S and 18‐S RNA from the 3′ end of the 23‐S RNA. These RNA's were reconstituted with total 50‐S subunit proteins and single binding proteins and the assembled proteins were identified. The results of each of these experimental approaches were in excellent agreement, and enabled us to position 22 proteins within three main sections of the 23‐S RNA.