Structural Plasticity of a Human G Protein‐Coupled Receptor Studied by NMR Spectroscopy

Abstract

The human genome encodes for 826 G protein‐coupled receptors (GPCRs), which are involved in nearly every physiological process and comprise the largest class of “druggable” proteins. Using nuclear magnetic resonance (NMR) in solution, we provide a global view of structural plasticity underlying the function of the human A2Aadenosine receptor (A2AAR), a representative class A human GPCR. To apply NMR to study a human GPCR we developed a robust molecular biology pipeline for production and sample preparation of stable‐isotope labeled receptors, yielding reproducible high‐quality NMR data. From these data, assignment of endogenous residues provided numerous probes distributed over the receptor intracellular surface, extracellular surface, and transmembrane domain, enabling a global characterization of A2AAR responses to variable efficacy of bound drugs. The NMR probes also permitted novel insights into changes in the local conformation of conserved GPCR activation motifs. In addition, we observed multiple local efficacy‐related conformers at the intracellular surface, which we relate directly to G protein signaling. The distributed NMR probes provide novel information on the role of a highly conserved GPCR allosteric center, permitting us to study the effect of this center on signaling pathways in the receptor. Amino acid replacement of the allosteric center caused striking changes in conformational polymorphisms at the intracellular surface but did not alter response to drug efficacy at the extracellular surface. We correlated changes at the intracellular surface to structural rearrangements at the toggle switch tryptophan and a conserved activation motif, providing novel insights into a widespread signaling mechanism in class A GPCRs. The presented work opens the door to exciting future studies of GPCR function, including studies of GPCRs in native environments.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.