Abstract
Ultraviolet inactivation of Escherichia coli ribosomes was studied by examining poly U-directed specific binding of phenylalanyl-tRNA and polyphenylalanine synthesis. The principal findings were as follows: 1. 1. The function of specific binding was inactivated according to single-hit type kinetics as is the case for polypeptide synthesis. Inactivation rates of these two functions in the 70-S ribosomes were almost identical. 2. 2. Inactivation of the specific binding activity in the 70-S ribosome is mainly due to damage in the 50-S sub-unit as is also the case for polyphenylalanine synthesis. 3. 3. When the 50-S sub-unit was irradiated in the isolated state, its enhancing effect on the specific binding was little affected but polyphenylalanine synthesis was inactivated. The results in 1–3 suggest that the functional sites in the 50-S sub-unit responsible for the specific binding activity might take different structures in the isolated 50-S sub-unit than in the 50-S sub-unit bound with the 30-S sub-unit. 4. 4. When the 30-S sub-unit was irradiated in the isolated state, the two activities were inactivated at different rates, the rate of the inactivation of the specific binding being slower. 5. 5. Binding of poly U or poly A to the 70-S ribosome induced no change in the ultraviolet sensitivity of the ribosome as measured by the specific binding activity.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call