Figure 1. Model of the Rho–GRK1 complex.

GRK1 modeled in a closed conformation with an ordered N–terminal helix is docked to Rho* using the C–terminal helix of Gα_s present in the β₂AR–G_s crystal structure as a guide ^{16, 33}. The coordinates for the model, in Protein Data Bank format, are available upon request. Positions of the ordered N– and C–termini are labeled with N and C, respectively. Domains of GRK1 are represented as follows: N–terminus region (Ser¹–Pro⁴²) in green, the RH domain in pink (Pro⁴³ to Glu¹⁸⁴ and Trp⁵¹⁵ to Arg⁵³²) and the kinase domain small lobe in brown (Asp¹⁸⁵ to Asn²⁶⁸) and large lobe in orange (Gly²⁶⁹ to Pro⁵¹⁴). The C–terminal region of GRK1 is shown in gray. The GRK1 model was constructed using a homology modeling strategy based on the X–ray of the GRK6 structure ¹⁵. The expected position of the lipid bilayer relative to the Rho*–GRK1 complex is illustrated by the grey rectangle. In this cartoon, a theoretical Rho*–Rho heterodimer is shown in red, based on the recently modeled H8–H8 dimer orientation, although monomeric Rho is also an efficient substrate for GRK1 in vitro ^34–36. All–trans–retinylidene and 11–cis–retinylidene are depicted using yellow and brown spheres, respectively.