Figure 5.

Cross-linking experiments using catalysts or MTS cross-linkers. A, Sandwich ELISA of secreted Aβ from APPNL-stable DKO cells transiently transfected with double-Cys mt PS1 (n = 3, mean ± SEs). Cross-linking experiments of double-Cys mt PS1 with Cys mutations in TMD4 or TMD5 and L383C (B), I387C (C), L435C, or D450C (D). Immunoblot analysis was performed using an anti-G1Nr5 antibody. PS1 NTFs and cross-linked products (NTF–CTF heterodimers) are shown by black arrowheads and black arrows, respectively. Double-Cys mt PS1s that failed to be cross-linked were shown in E. The predicted maximum lengths between two residues are indicated as red lines in the schematic illustrations on the right. Residues mutated to Cys are shown by circles. Positions of cross-linked cysteines were indicated by green circles. Predicted structure of the catalytic pore and distances between cross-linked residues were indicated by blue lines and red arrows, respectively. Positions of catalytic aspartates and conserved motifs were shown by stars and white circles, respectively.