English: The human gamma-secretase protein complex solved by cryo-electron microscopy, containing nicastrin (red), presenilin-1 (orange), PEN-2 (blue), and APH-1 (green). The complex is located in the membrane of the endoplasmic reticulum, whose lumenal side is shown in red and cytoplasmic side in blue. Gamma-secretase is the protease responsible for processing amyloid precursor protein (APP) to Aβ peptide.

Image rendered using PyMol from PDB ID 5A63:

Xiao-chen Bai, Chuangye Yan, Guanghui Yang, Peilong Lu, Dan Ma, Linfeng Sun, Rui Zhou, Sjors H. W. Scheres, Yigong Shi. (2015). An atomic structure of human γ-secretase. Nature 525, 212–217 (10 September 2015) doi:10.1038/nature14892.