Structural transitions of transmembrane helix 6 in the formation of metarhodopsin I.

ABSTRACT: Absorption of light by the visual pigment rhodopsin triggers a rapid cis-trans photoisomerization of its retinal chromophore and a series of conformational changes in both the retinal and protein. The largest structural change is an outward tilt of transmembrane helix H6 that increases the separation of the intracellular ends of H6 and H3 and opens up the G-protein binding site. In the dark state of rhodopsin, Glu247 at the intracellular end of H6 forms a salt bridge with Arg135 on H3 to tether H6 in an inactive conformation. The Arg135-Glu247 interaction is broken in the active state of the receptor, and Arg135 is then stabilized by interactions with Tyr223, Met257, and Tyr306 on helices H5, H6, and H7, respectively. To address the mechanism of H6 motion, solid-state NMR measurements are

SUBMITTER: Eilers M 

PROVIDER: S-EPMC3428503 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature