Model of the rhodopsin-G protein interface showing nitroxide labeling sites as red Cα carbon spheres. Dotted lines indicate the DEER distance measurements that were made between receptor and G protein. The gray ribbon is the rhodopsin backbone, while the green, cyan, and magenta ribbons identify the Ras-like domain of the Gα-subunit, the Gβ-subunit, and the Gγ-subunit, respectively.

Ned Van Eps in the Ernst laboratory used DEER spectroscopy together with molecular modeling techniques to map the structure of a complex between a G-protein-coupled receptor (GPCR) and its G protein. A paper describing the methodology used for characterizing the binding interface of the rhodopsin–G protein complex has recently been published in PNAS. The authors discovered that the binding mode of G protein subtypes is distinct and key differences suggest features of GPCR selectivity.