Abstract
G-protein coupled receptors (GPCRs) constitute the largest family of integral membrane proteins, mediating a vast array of physiological processes and serving as primary targets for approximately one-third of all marketed drugs. Elucidating the precise structural mechanisms governing GPCR activation and G-protein coupling is paramount for advancing rational drug design. Traditional structural biology techniques often necessitate the removal of GPCRs from their native lipid environments, potentially obscuring critical lipid-protein interactions fundamental to their function. This study leverages the transformative power of cryo-electron microscopy (cryo-EM) to resolve the high-resolution structure of a prototypical GPCR-G protein signaling complex directly reconstituted into native-like lipid bilayers. Our methodology involved the expression and purification of a representative GPCR, its functional reconstitution into proteoliposomes mimicking cellular membranes, and subsequent formation of an active agonist-bound G-protein complex. High-resolution cryo-EM data enabled the 3D reconstruction of the complex, revealing unprecedented details of the GPCR-G protein interface and, crucially, the specific influence of surrounding lipids on receptor conformation and G-protein engagement. We identify discrete lipid densities interacting with the GPCR transmembrane bundle, suggesting an allosteric role for lipids in modulating receptor activation. These findings underscore the critical importance of studying GPCR signaling within a native lipid context, offering a more physiologically relevant understanding of receptor dynamics and providing novel avenues for therapeutic intervention.
Keywords
GPCR, Cryo-EM, G-protein, Lipid environment, Structural biology, Membrane proteins, Signal transduction, Drug discovery