Figure 1
GRK2 and RGS2/8 contain a structurally similar RH domain that binds to non-overlapping surfaces of Gαq via different sub-structures of the RH domain. (a) Superimposition of the structures of RGS2 and GRK2 (from PDB IDs: 4EKD and 2BCJ, respectively). The structurally-aligned core of the RGS2 and GRK2 RH domains are colored blue and purple, respectively. Two helices in the N- and C-terminal regions of the GRK2 RH domain that do not have equivalent sub-structures in RGS2 (GRK2 residues 36–52 and 513–553) are colored red and maroon, respectively, while the unaligned parts of GRK2 are colored gray. (b) Superimposition of the Gαq-RGS2, Gαq-RGS8 and Gαq-GRK2 complexes (PDB IDs: 4EKD, 5DO9 and 2BCJ, respectively), using only the coordinates of Gαq. Gαq subunits are visualized as ribbon diagrams, colored orange (GTPase domain) and yellow (helical domain). GRK2 and RGS2/8 are colored as in panel a and the three Gαq partners are also visualized as transparent molecular surfaces. (c) The binding pose of the GRK2 RH domain relative to the GTPase domain of Gαq, shown as in panel b, with GRK2 helices α5 and α6 colored green and magenta, respectively. (d) The binding pose of the RGS2 and RGS8 RH domains, relative to Gαq, shown as in panel b but rotated 90° about the X-axis. RGS helices are numbered, with the RGS2 and RGS8 α5 and α6 helices colored green and magenta, as the corresponding GRK2 helices in panel c.
