Figure 6. The requirement for BiP is signal sequence dependent.

A. HeLa cells were pre-incubated with recombinant SubAB or its inactive mutant, SubA_A272B, and the resulting BiP cleavage confirmed via a molecular weight shift from the full-length form (BiP_NC) to a lower molecular weight species (BiP_N). The intact BiP content of cells treated with the active form of SubAB is expressed relative to those treated in parallel with the inactive mutant, and the accompanying graph shows the means (±s.e) for n = 3. B to G. HeLa cells were treated with the cytotoxin AB₅ subtilase (SubAB) or an inactive mutant (SubA_A272B), precursor proteins (as Figures 3 and 4) synthesized in the presence of the resulting semi-intact cells, and samples analyzed by quantification as before (see Figures 3 and 4). All results are given as means (±s.e) where n = 3 (panels F and G), n = 4 (panels B and C) or n = 5 (panels D and E).