Figure 1.

Ribbon and surface representations of ERAP1, ERAP2, and IRAP as revealed from the recent crystallographic studies. (A,B) ERAP1 complexes with the aminopeptidase inhibitor, bestatin, in the “closed” and “open” states, (C) ERAP2 and (D) IRAP complexes with a phosphinic pseudopeptidic inhibitor that is shown with orange colored spheres. For clarity, bestatin was omitted from the structures of ERAP1. The four domains are labeled and color-coded as cyan for domain I, blue for domain II, yellow for domain III, and red for domain IV. The catalytic zinc is shown as a pink sphere and the polymorphic site residues are indicated with green colored spheres. The modeled regions in ERAP1 that were not determined in the X-ray structures are shown in gray.