Measuring rhodopsin-G-protein interactions by surface plasmon resonance.

G-protein-coupled receptors (GPCRs) initiate a variety of cellular responses to diverse array of extracellular stimuli. Surface plasmon resonance detection offers a powerful approach to the study of protein-protein interactions in real time. In this chapter we outline procedures for the immobilization of the prototype GPCR structure, rhodopsin or the G-protein alpha and betagamma subunits, for analysis of the molecular interactions initiating G-protein signaling. The attachment of rhodopsin via its extracellular carbohydrate residues provides a convenient, and universally applicable, procedure for GPCR immobilization in a form that retains full biochemical activity and ability to interact with intracellular signaling components. SPR detection then allows for the analysis of the kinetic and equilibrium binding properties of the immobilized receptor with G-protein subunits and potentially other interacting molecules.