Fig. 2.

Homology between APH-1 and type II CAAX protease homolog. The structures of type II CAAX protease homolog (pdb: 4CAD, chain C) and γ-secretase subunit APH-1 (pdb: 5A63, chain C) are shown in panels a and b, respectively. Six core TM segments shared between them are colored blue, cyan, green, yellow, orange, and red from N- to C-terminus. Sidechains of conserved polar residues inside membrane are shown, including EExxxR motif in core TM segment 2 and two histidines in core TM segments 3 and 5 for type II CAAX protease homolog and QExxR motif in TM segment 2 and two histidines in core TM segments 4 and 5 for APH-1