화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.123, No.43, 9134-9142, 2019
Conformational Differences among Metarhodopsin I, Metarhodopsin II, and Opsin Probed by Wide-Angle X-ray Scattering
Among the photoproducts of vertebrate rhodopsin, only metarhodopsin II (Meta-II) preferentially adopts the active structure in which transmembrane helices are rearranged. Light-induced helical rearrangement of rhodopsin in membrane-embedded form was directly monitored by wide-angle X-ray scattering (WAXS) using nanodiscs. The change in the WAXS curve for the formation of Meta-II was characterized by a peak at 0.2 angstrom(-1) and a valley at 0.6 angstrom(-1), which were not observed in metarhodopsin I and opsin. However, acid-induced active opsin (Opsin*) showed a 0.2 angstrom(-1) peak, but no 0.6 angstrom(-1) valley. Analyses using the model structures based on the crystal structures of dark state and Meta-II suggest that the outward movement of helix VI occurred in Opsin*. However, the displaced helices III and V in Meta-II resulting from the disruption of cytoplasmic ionic lock were restored in Opsin*, which is likely to destabilize the G-protein-activating structure of opsin.