Figure 3. V₂Rpp interactions with β-arrestin1.

a, Overall view of β-arrestin1, with regions of interest in boxes. Select charge-charge contacts are shown in dotted lines. b, V₂Rpp (green) displaces the inactive finger loop (light blue), causing it to adopt an extended conformation in the active state (gold). c, In the inactive conformation, the β-arrestin1 carboxy-terminal β strand (dark blue) lies along the N-domain in the “three element” interaction network. d, Upon activation, this strand is displaced by the carboxy terminus of the V₂Rpp, which engages in extensive charge-charge interactions through phosphorylated residues. e, The “polar core” of β-arrestin1 is thought to be a critical stabilizer of the inactive state. f, Upon V₂Rpp binding, the carboxy-terminal strand residue Arg393 is displaced, and its interaction partner D297 undergoes a large movement together with the rest of the lariat loop.