Figure 3.

BACE2 cleaves Aβ(1–28) following Phe-19 and Phe-20. HEK293T cells were transfected with vector alone, C-terminally tagged BACE1, or C-terminally tagged BACE2 as indicated, lysed, and precipitated with 1D4-Sepharose beads. Beads were washed and incubated with 50 μM Aβ(1–28) peptide and analyzed by TOF-MALDI. ++, Double protonation of the indicated peptide. Peaks at 1196.5, 2314.2, and 2461.2 Da correspond to N-terminal peptide fragments cleaved after Aβ residues 10, 19, and 20, respectively. Peaks at 2083.6 and 966.5 Da correspond to the C-terminal peptide fragments cleaved before residues 11 and 20, respectively. The peptide sequence with APP and Aβ numbering is displayed below the figures.