Chapter 2. Insights into GPCR Activation from NMR Spectroscopy

Abstract

This review summarizes the progress made using solid-state magic angle spinning NMR spectroscopy as a tool for probing G protein-coupled receptor structure and activation. It focuses on rhodopsin, the dim-light photoreceptor in vertebrates. The vitamin A retinal chromophore is the photoreactive group in rhodopsin. It is covalently bound to the receptor, functions as a pharmacological inverse agonist in the 11-cis configuration in the dark and is rapidly converted by light to the all-trans configuration, which functions as a full agonist. The expression methods for incorporation of stable 13C and 15N isotopes into G protein-coupled receptors and the NMR methods for measuring internuclear distances are described. Finally, the progress made using NMR spectroscopy to characterize the conformation and environment of the retinal chromophore, and the structural changes that occur upon light activation of the receptor, are reviewed.