This is the x-ray crystal structure of bovine rhodopsin, the 7-span G-protein linked receptor that starts the transduction of photons to electrical impulses. The chromophore that captures the photon, retinal, is also in the structure. Rhodopsin binds its G-protein's alpha subunit via rhodopsin's C-terminal tail from residues 325-338, of which only four residues are resolved in this crystal structure. The data file is 2I35 from the Protein Data Bank.