Site of action of RNase I on the 50 S ribosome of Escherichia coli and the association of the enzyme with the partially degraded subunit

Abstract

The 50 S ribosome of Escherichia coli is partially degraded by RNase I in presence of a high concentration of Mg²⁺ (10 to 20 mM); the partially degraded subunit becomes resistant to the further action of RNase I. The latter remains latent in association with the subparticle as in case of 30 S ribosome (Neu, H.C., and Heppel, L.A. (1954) Proc. Natl. Acad. Sci. U.S.A. 51, 1267-1274). As a result of nucleolytic action, 23 S RNA is degraded to a smaller size and four proteins (L4, L10, L7/L12) are released from the subunit. From the location of these proteins, it appears that the primary site of action of RNase I is the central protuberance of the armchair model proposed for the subunit (Stoffler, G., and Whitman, H.G. (1977) in Molecular Mechanisms of Protein Biosynthesis (Weissbach, H., and Pestka, S., eds) pp. 117-144, Academic Press, New York).