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. Author manuscript; available in PMC: 2016 Jan 30.
Published in final edited form as: Nature. 2015 Jul 22;523(7562):561–567. doi: 10.1038/nature14656

Figure 6. Structural basis of arrestin-biased signaling and arrestin recruitment.

Figure 6

a–b, Two views of structural overlays of arrestin-bound rhodopsin (green) with inactive rhodopsin (pink).

c–d, Two views of structural overlays of arrestin-bound rhodopsin (green) with GαCT peptide-bound rhodopsin (orange).

e, A cartoon model of arrestin recruitment by a phosphorylated and active rhodopsin. In the dark state, the receptor is inactive (R-state) and arrestin is in the closed state (basal state). Receptor activation and phosphorylation (P-R* state) allow the phosphorylated C-terminal tail of rhodopsin to bind to the N-domain of arrestin (pre-activated state), thus displacing the arrestin C-terminal tail. This displacement destabilizes the polar core of arrestin, which allows a 20° rotation between the arrestin N- and C- domains, leading to the opening of the middle loop (ML) and lariat loop (LL) to accommodate the ICL2 helix of rhodopsin (fully-activated state). The activated receptor also opens the cytoplasmic side of the TM bundle to adopt the finger loop (FL) of arrestin.