Requirement of an Escherichia coli 50 S Ribosomal Protein Component for Effective Interaction of the Ribosome with T and G Factors and with Guanosine Triphosphate

Abstract Escherichia coli ribosomes were made deficient in a 50 S ribosomal protein component by treatment with ethanol and NH4Cl and their ability to carry out a number of partial reactions involved in polypeptide synthesis was examined. The ribosomes were found to be competent in all reactions in which the ribosome alone participated, but were markedly deficient in all reactions involving an interaction of the ribosome, GTP, and either of the supernatant factors T and G. Nonenzymatic phenylalanyl-tRNA and N-acetylphenylalanyl-tRNA binding and the peptidyl transferase activity were essentially intact in these ribosomes; enzymatic binding of phenylalanyl-tRNA and translocation occur, but at markedly reduced rates; uncoupled GTPase activity associated with G factor and the ability to bind 3HGTP in the presence of G factor and fusidic acid were virtually abolished; and uncoupled GTPase activity associated with T factor was diminished to about 15% of the activity present with unextracted ribosomes. Polyphenylalanine synthesis and all the partial reactions were completely or substantially restored by readdition of the ribosomal extract.