Rhodopsin transmembrane segment interactions

Binding of these ligands does not occur in a concave groove located on the surface of the receptor protein as otherwise often imagined. As described in Section 2.2.1, the x-ray structure of rhodopsin showed that retinal is bound deep in the seven-helical structure with major interaction points in TM-III and TM-VI, as well as the covalent attachment point in TM-VII. In fact, rhodopsin interacts with basically all transmembrane segments. Importantly, side-chains from the transmembrane helices cover the retinal molecule on all sides, and its binding site is found deep in the middle of... 

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