Ribosomal Protein - Proteins in E. Coli Ribosomes

Proteins in E. Coli Ribosomes

The ribosome of E. coli has about 22 proteins in the small subunit (labelled S1 to S22) and 34 proteins in the large subunit (L1 to L36). All of them are different with three exceptions: one protein is found in both subunits (S20 and L26), L7 and L12 are acetylated and methylated forms of the same protein, and L8 is a complex of L7/L12 and L10. In addition, L31 is known to exist in two forms, the full length at 7.9 kilodaltons (kDa) and fragmented at 7.0 kDa. This is why the number of proteins in a ribosome is of 56. Except for S1 (with a molecular weight of 61.2 kDa), the other proteins range in weight between 4.4 and 29.7 kDa.