Interaction of the C-Terminal Region of the Gγ Protein with Model Membranes

Heterotrimeric G-proteins interact with membranes. They accumulate around membrane receptors and propagate messages to effectors localized in different cellular compartments. G-protein-lipid interactions regulate G-protein cellular localization and activity. Although we recently found that the Gβγ dimer drives the interaction of G-proteins with nonlamellar-prone membranes, little is known about the molecular basis of this interaction. Here, we investigated the interaction of the C-terminus of the Gγ2 protein (Pγ-FN) with model membranes and those of its peptide (Pγ) and farnesyl (FN) moieties alone. X-ray diffraction and differential scanning calorimetry demonstrated that Pγ-FN, segregated into Pγ-FN-poor and -rich domains in phosphatidylethanolamine (PE) and phosphatidylserine (PS) membranes. In PE membranes, FN increased the nonlamellar phase propensity. Fourier transform infrared spectroscopy experiments showed that Pγ and Pγ-FN interact with the polar and interfacial regions of PE and PS bilayers. The binding of Pγ-FN to model membranes is due to the FN group and positively charged amino acids near this lipid. On the other hand, membrane lipids partially altered Pγ-FN structure, in turn increasing the fluidity of PS membranes. These data highlight the relevance of the interaction of the C-terminal region of the Gγ protein with the cell membrane and its effect on membrane structure.