Enzymatic activity of highly purified γ-secretase complexes with FAD-linked or aspartate PS1 mutants.
Equal amounts of the different purified γ-secretase preparations characterized in Figure 4 were tested for activity on C100-Flag, as described in Figure 3. The resulting cleavage products were separated by SDS-PAGE and detected by immunostaining with an anti-Flag antibody (M2) for C100-Flag or AICD-Flag (A), and by sandwich ELISA for Aβ1–40 or Aβ1–42 (B). Note that the levels of Aβ produced from FAD-linked γ-secretase complexes were all in the non-linear range of the ELISA standards, close to the detection limit. Whenever possible, Aβ1–42/Aβ1–40 ratios were quantified and indicated on the top of the bars. Two independent purifications were performed on each clone and similar results were obtained. A representative dataset is shown.