Effects of ribosomal mutations on the read-through of a chain termination signal: studies on the synthesis of bacteriophage lambda O gene protein in vitro.

In a DNA-dependent protein-synthesizing system that contains streptomycin-sensitive ribosomes, lambda DNA directs the synthesis of two proteins that are products of the O gene. The larger is produced as a result of read-through of a UGA termination codon. In the system containing streptomycin-resistant ribosomes this read-through protein is not synthesized, indicating that the mutational alteration in the ribosomal protein S12 restricts the read-through. The mutant ribosomes also fail to synthesize the read-through coat protein of RNA phage Qbeta. In addition, the mutant ribosomes restrict suppression of amber mutations in vitro, similar to their effect in vivo.