Functional reconstitution of β 2 -adrenergic receptors utilizing self-assembling Nanodisc technology

Integral membrane G protein-coupled receptors (GPCRs) compose the single most prolific class of drug targets, yet significant functional and structural questions remain unanswered for this superfamily. A primary reason for this gap in understanding arises from the difficulty of forming soluble, monodisperse receptor membrane preparations that maintain the trans-membrane signaling activity of the receptor and provide robust biophysical and biochemical assay systems. Here we report a technique for self-assembling functional 2 -adrenergic receptor (β 2 AR) into a nanoscale phospholipid bilayer system (Nanodisc) that is highly soluble in aqueous solution. The approximately 10-nm nanobilayer particles contain β 2 AR in a native-like phospholipid bilayer domain of approximately 100 phospholipid molecules circumferentially bound by a membrane scaffold protein (MSP). The resulting construct allows for access to the physiologically intracellular and extracellular faces of the receptor and thus allows unrestricted access of antagonists, agonists, and G proteins. These Nanodisc-solubilized GPCRs can be directly purified by normal chromatographic procedures. We define the resultant Nanodisc-embedded monomeric β 2 AR by antagonist and agonist binding isotherms and demonstrate faithful G protein coupling.