3B4R:
reference: Structure of a site-2 protease family intramembrane metalloprotease., Feng L, Yan H, Wu Z, Yan N, Wang Z, Jeffrey PD, Shi Y, Science. 2007 Dec 7;318(5856):1608-12. PMID: 18063795

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).