Western analysis of extracts and ribosomes from cells synthesizing the indicated L4 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 a 15% PAGE gel and subjected to Western analysis using antibodies to the Strep tag (a-Strep) followed by L4 antisera (a-L4). The relative amount of induced L4–Δloop protein was calculated from the anti-L4 Western by dividing the signal in the deletion protein by the total signal in deletion and wild-type (chromosome-derived) protein, and then normalizing the ribosome values to the induced extract value. The amount of induced wild-type L4 was calculated by dividing the signal from the Strep antibody (plasmid-derived L4) by the value from the L4 antibody (chromosome- and plasmid-derived L4), again normalizing to the extract value.
