Oligomeric state of rhodopsin within rhodopsin-transducin complex probed with succinylated concanavalin A.

Rhodopsin-a prototypical G protein-coupled receptor (GPCR)-is abundantly expressed in the eye and stabilized by its covalently bound chromophore 11-cis-retinal. The signal of light is amplified and transmitted through the binding of heterotrimeric G protein transducin (G t ) to photoactivated rhodopsin following downstream pathways activation leading to light sensing in the brain. As demonstrated by atomic force microscopy (AFM), rhodopsin exists in the native membrane of the rod outer segment disks as dimers highly organized in tightly packed oligomers. However, functional importance of this organization is still debated. To clarify the role of the rhodopsin dimer in signaling activation and thus the binding of transducin, the complex between rhodopsin and transducin can be formed, purified, and probed with succinylated concanavalin A. This method can be potentially applied to other GPCRs to verify their oligomeric state.