Figure 1. Identification of the putative sigma 2 receptor binding site as PGRMC1 using a novel photoaffinity probe.
a, WC-21 contains a FITC group and a photoactive azide (N3) moiety, and displays high sigma-2 receptor affinity and selectivity; Ki = 8.7 ± 1 nM for sigma-2 receptor and Ki > 4,000 nM for sigma-1 receptor. b, Following UV cross-linking, ligand-labeled proteins were enriched and separated through SDS-PAGE; WC-21 cross-linked proteins can be visualized using an anti-FITC antibody; SS is silver staining and WB is western blot. c, Proteomic studies of the FITC positive band identified two proteins which shared the same genetic name: progesterone receptor membrane component 1 (PGRMC1). The protein structure shows the peptides (bold) detected by mass spectrometry as well as the Cytochrome b5 domain (underlined).