Expression, Purification and Crystallisation of the Adenosine A Receptor Bound to an Engineered Mini G Protein.

G protein-coupled receptors (GPCRs) promote cytoplasmic signalling by activating heterotrimeric G proteins in response to extracellular stimuli such as light, hormones and nucleosides. Structure determination of GPCR-G protein complexes is central to understanding the precise mechanism of signal transduction. However, these complexes are challenging targets for structural studies due to their conformationally dynamic and inherently transient nature. We recently developed an engineered G protein, mini-G, which addressed these problems and allowed the formation of a stable GPCR-G protein complex. Mini-G facilitated the structure determination of the human adenosine A receptor (AR) in its G protein-bound conformation at 3.4 Å resolution. Here, we describe a step by step protocol for the expression and purification of AR, and crystallisation of the AR-mini-G complex.