CHRIS TATE

STRUCTURE OF THE ADENOSINE A2A RECEPTOR BOUND TO AN ENGINEERED G PROTEIN

G protein-coupled receptors (GPCRs) activate intracellular signalling proteins (G proteins and arrestins) in response to extracellular signalling molecules. GPCRs are highly dynamic proteins, which rapidly interchange between different conformational states. In order to understand the molecular mechanisms of GPCR activation, and to facilitate efficient drug design, structures of GPCRs in all conformational states are required. Unsurprisingly, ternary complexes, involving native signalling proteins, have proved most difficult to crystallise due to their instability. We have developed an engineered G protein, which is significantly more stable in complex with GPCRs than native Gs. Engineered Gs is particularly stable in short chain detergents and thus suitable for crystallisation of GPCR – G protein complexes by vapour diffusion. Additional components, such as nanobodies, are not required for maximal stability. We have purified complexes of engineered Gs with both the adenosine A2a receptor (A2aR) and β1-adrenergic receptor (β 1AR) and have determined the structure of wild type human A2aR bound to engineered Gs at 3.4 Å resolution by X ray crystallography. The structure will be presented, compared to the β2-adrenergic receptor-Gs complex and implications for GPCR signalling discussed.