The Conformational Equilibrium of the Neuropeptide Y2 Receptor in Bilayer Membranes

Abstract

Dynamic structural transitions within the seven-transmembrane bundle represent the mechanism by which G-protein-coupled receptors convert an extracellular chemical signal into an intracellular biological function. Here, the conformational dynamics of the neuropeptide Y receptor type 2 (Y2R) during activation was investigated. The apo, full agonist-, and arrestin-bound states of Y2R were prepared by cell-free expression, functional refolding, and reconstitution into lipid membranes. To study conformational transitions between these states, all six tryptophans of Y2R were ¹³ C-labeled. NMR-signal assignment was achieved by dynamic-nuclear-polarization enhancement and the individual functional states of the receptor were characterized by monitoring ¹³ C NMR chemical shifts. Activation of Y2R is mediated by molecular switches involving the toggle switch residue Trp281^6.48 of the highly conserved SWLP motif and Trp327^7.55 adjacent to the NPxxY motif. Furthermore, a conformationally preserved "cysteine lock"-Trp116^23.50 was identified.

Keywords: NMR spectroscopy; arrestin; molecular switch; receptors; structural dynamics.