Fig. P1.

The orientation of the GRK2-Gβ₁γ₂ complex (inset) can be studied using SFG vibrational spectroscopy. Spectra were collected from samples of protein in contact with a 9∶1 POPC/POPG lipid bilayer. Based on analysis of fitted spectral intensity ratios in spectra collected using different laser polarizations, it was found that the orientation of GRK2-Gβ₁γ₂ did not match that predicted from the crystal structure alone. A possible membrane orientation (shown) is consistent with the presence of a GPCR docking site homology modeled from the structure of GRK6. The protein, lipid bilayer, SFG beams, the prism, and the sample container are not drawn to scale.