[18] Measuring cooperative binding between retinal rod G protein, transducin, and activated rhodopsin

Publisher Summary This chapter describes a method for labeling G t and measuring light-induced association of G t with Rho* in rod disk membranes. As molecular cloning techniques make a variety of G proteins and their receptors available in larger quantities, this approach may become more widely applicable to the study of receptor-G protein interactions. Among the many questions that will be addressed is whether cooperative interactions are a general feature of receptor-G protein binding or whether they are specific to Rho* and G t . The unique ability of rods to amplify and detect very small signals constitutes one of the most remarkable examples of G-protein-dependent signal transduction. There are number of purification schemes for G tα and G tβγ . The procedures described are a modification of those purification schemes, which have found to give consistently high yields of very pure G ta and G tβγ without detectable loss in activity.