Fig. 3.

Hydrolysis FTIR spectra of intrinsic and RGS4-catalyzed Gα_i1-WT and its mutant R178S. RGS4 shifted the α-GTP vibration from 1,243 cm⁻¹ to 1,184 cm⁻¹. The effect was reversible when Arg178 was mutated. Full spectra of the photolysis and the hydrolysis reaction are depicted in SI Appendix, Fig. 5.