“Structure of a presenilin family intramembrane aspartate protease,” by Xiaochun Li, Shangyu Dang, Chuangye Yan, Xinqi Gong, Jiawei Wang & Yigong Shi (Vol. 493, No. 7430, January 2, 2013, p. 56-61).
www.nature.com/nature/journal/v493/n7430/abs/nature11801.html
