Phosducin (Phd)-like family, Phd subfamily; Phd is a cytosolic regulator of G protein functions. It specifically binds G protein betagamma (Gbg)-subunits with high affinity, resulting in the solubilization of Gbg from the plasma membrane. This impedes the formation of a functional G protein trimer (G protein alphabetagamma), thereby inhibiting G protein-mediated signal transduction. Phd also inhibits the GTPase activity of G protein alpha. Phd can be phosphorylated by protein kinase A and G protein-coupled receptor kinase 2, leading to its inactivation. Phd was originally isolated from the retina, where it is highly expressed and has been implicated to play an important role in light adaptation. It is also found in the pineal gland, liver, spleen, striated muscle and the brain. The C-terminal domain of Phd adopts a thioredoxin fold, but it does not contain a CXXC motif. Phd interacts with G protein beta mostly through the N-terminal helical domain.
Feature 1:G protein beta interface [polypeptide binding site]
Evidence:
Structure:1B9YC, Rattus norvegicus Phosducin binds Transducin beta; contacts at 3.5A
Comment:Most of the binding energy comes from the N-terminal helical domain of phosducin with a lesser contribution from the C-terminal TRX-like domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",