Western analysis of extracts and ribosomes from cells synthesizing L22 derivatives. Extracts from uninduced and induced cells (ext − and ext +, respectively) and crude and salt-washed ribosomes from induced cells (cr rib and sw rib, respectively) were fractionated on 10% Tricine gels and subjected to Western analysis using anti-sera to the Strep-tag on L22 (a-strep), followed by antisera to L4 (a-L4). The relative amount of induced L22 wild-type or mutant protein was calculated by dividing the signal in L22 (detected by anti-Strep) by the signal in the chromosome-derived L4 protein (detected by anti-L4). Resulting values for crude and salt-washed ribosomes were then normalized to the value in the corresponding induced extract. The band identified as x is a protein cosedimenting with ribosomal particles and recognized by the Strep-tag polyclonal antibody.
