Improved electrophoretic and immunochemical techniques for the identification and characterization of mutant proteins, applied to ribosomal protein S8 in Escherichia coli mutants.

The ribosomal proteins of 11 mutants which are sensitive to starvation at elevated temperature and of 36 transductants derived from them were studied with several electrophoretic, immunochemical and proteinchemical methods. The following results were obtained: (1) Ribosomal protein S8 is altered in three of these mutants. (2) The amino acid exchange in proteins S8 of mutant N4128 is Glu leads to Lys in position 59 of the protein chain. (3) Temperature sensitivity and inability to recover from starvation at elevated temperatures are caused by the same mutational event which is, however, unrelated to the alteration in protein S8. Several electrophoretic and immunological procedures were applied during the characterization of these mutants. A modified immunoelectrophoresis on cellulose acetate gels was developed, and proved to be the most applicable procedure for the detection of mutationally altered ribosomal proteins. This procedure may gain general importance for detecting mutational alterations in other proteins.