FIGURE 4.

Probing ligand–receptor interaction on mammalian cells. Photo‐cross‐linking unnatural amino acid (Uaa) Azi was incorporated into corticotropin releasing factor receptor type 1 (CRF1R) to reveal the binding pocket (in purple) for its peptide agonist Ucn1; Latent bioreactive Uaa F_fact was incorporated into CRF1R together with Cys in Ucn1 to determine reciprocal spatial constrains (circle with same colors) of the receptor–ligand complex. These data, obtained from intact receptor expressed in live cells, were then integrated to build a conformation model for full‐length CRF1R in complex with Ucn1