| Abstract: | We have used the application of hydrostatic pressure to modify the misreading of polyuridylate template. Pressure was used to test ribosomes isolated from Escherichia coli strains containing mutations in the S12 ribosomal protein which lead to streptomycin-resistance and -dependence. The incorporation of phenylalanine into polypeptide, at a given pressure, was found to vary with the source of ribosomes and was found to correlate with S12-dependent changes in rates of incorporation suggesting a role of the S12 ribosomal protein in the pressure effect. Streptomycin partially alleviated the increased pressure-resistance in those cases where control rates of incorporation were found to be stimulated by the addition of streptomycin. In contrast, the misincorporation of isoleucine was substantially more sensitive to pressure application, regardless of ribosome source or the presence of streptomycin. These results suggest that the application of hydrostatic pressure affects at least two distinct ribosomal reactions important to the discrimination of these two amino acids. |
