Molecular Morphology of Ribosomes

Using the lactoperoxidase‐catalyzed iodination system as a probe for exposed proteins, the location of ribosomal proteins on 50‐S subunits of Escherichia coli was examined. These studies demonstrated that at least three of the proteins in the 50‐S ribosome are iodinated and may be termed exposed proteins. Most of the proteins, on the other hand, are not iodinated and can be classified as buried or partially buried proteins. Unfolding of the 50‐S ribosome by the removal of Mg2+ resulted in a decreased organization of the ribosome structure and allowed all the proteins except one to be iodinated.