Radioligand Binding Analysis as a Tool for Quality Control of GPCR Production for Structural Characterization: Adenosine A2aR as a Template for Study

Functional characterization of G protein–coupled receptors is essential to ascertain the suitability of a protein target for downstream studies and to help develop optimal expression and isolation procedures. Radioligand binding analysis is a well-established technique, which allows direct measurement of the amount of functional receptor in a sample. It can be readily applied to both membrane-bound and soluble receptor samples and is an ideal method for monitoring the amount of functional protein at each stage in the expression and isolation process. This unit presents protocols for the radioligand binding analysis of the human adenosine A2a receptor and provides examples of how these assays can be used at several stages to help optimize expression, solubilization, and isolation procedures. Keywords: G protein–coupled receptor; adenosine A2aR; saturation radioligand binding assay; competitive radioligand binding assay; dissociation constant; specific activity