Figure 2.

Molecular characteristics of the GRK protein family. All GRKs (60-80KDa) possess a similar molecular structure with an α-N-terminal domain followed by an N-terminal Regulator of G protein Signaling domain (RGS/N), which is important for receptor recognition and intracellular membrane anchoring ¹⁵³, ¹⁵⁴. The protein kinase catalytic domain with a short AGC protein kinase domain is responsible for GRKs catalysis. The C-terminus has more motif variants than the RGS/C domain, which is critical for receptor recognition ¹⁴. Unlike other isoforms, the GRK2 subfamily (GRK2 and GRK3) has a pleckstrin homology domain (PH), which is important for terminating Gβγ complex-related downstream signaling. The C-terminus length varies among all GRK subtypes (~105 to 230 AAs).