Solvent accessibility of a GPCR transmembrane domain probed by in‐membrane chemical modification (IMCM)

Abstract

G protein‐coupled receptors (GPCRs) transmit signals from drugs across cell membranes, leading to associated physiological effects. To study the structural basis of the transmembrane signalling, in‐membrane chemical modification (IMCM) has previously been introduced for 19F‐labelling of GPCRs expressed in Spodoptera frugiperda (Sf9) insect cells. Here, IMCM is used with the A2A adenosine receptor (A2AAR) expressed in Pichia pastoris; 19F‐NMR revealed nearly complete solvent protection of the A2AAR transmembrane domain in the membrane and in 2,2‐didecylpropane‐1,3‐bis‐β‐D‐maltopyranoside (LMNG)/cholesteryl hemisuccinate (CHS) micelles, and extensive solvent accessibility for A2AAR in n‐dodecyl β‐D‐maltoside (DDM)/CHS micelles. No Cys residue dominated non‐specific labelling with 2,2,2‐trifluoroethanethiol. These observations yield an improved protocol for IMCM 19F‐labelling of GPCRs and new insights into variable solvent accessibility for function‐related characterization of GPCRs.