NMR Structure of the Second Intracellular Loop of the α2A Adrenergic Receptor: Evidence for a Novel Cytoplasmic Helix † , ‡

A major, unresolved question in signal transduction by G protein coupled receptors (GPCRs) is to understand how, at atomic resolution, a GPCR activates a G protein. A step toward answering this question was made with the determination of the high-resolution structure of rhodopsin; we now know the intramolecular interactions that characterize the resting conformation of a GPCR. To what degree does this structure represent a structural paradigm …