Electrophoretic and immunological studies on ribosomal proteins of 100 Escherichia coli revertants from streptomycin dependence

Summary Revertants from streptomycin dependence to independence were isolated as single step mutants from six different streptomycin dependent strains. The ribosomal proteins from 100 such mutants were analyzed by two-dimensional polyacrylamide gel electrophoresis and some of them were also examined by immunological techniques. Altered proteins were found in 40 mutants, 24 in protein S4 and 16 in protein S5. No change in any other protein was detected.Altered S5 proteins migrated into five different positions on the polyacrylamide plate and it can be concluded that the mutant proteins differ from the wild type probably by single amino acid replacements. The altered S4 proteins migrated into 17 different positions on the plate. Extensive changes of length, both shorter and longer than wild type S4 protein, are postulated for many of the mutant S4 proteins.Analysis of the ribosomal proteins of four ram mutants revealed altered S4 protein in two of them. The alterations in these mutant proteins are probably very similar to those found in streptomycin independent mutants.Among the revertants there was no apparent correlation between the protein alteration and the particular response to streptomycin.These studies suggest a strong interaction between protein S12, which confers streptomycin dependence, and protein S4 or S5, which can suppress this dependence.Paper No. 60 on Ribosomal Proteins. Preceding paper is by B. Wittmann-Liebold, Hoppe-Seyler's Z. physiol. Chemie, in press.