Retinal G-protein-coupled receptor

Hao W, Fong HK 1999 The endogenous chromophore of retinal G protein-coupled receptor opsin from the pigment epithehum. J Biol Chem 274 6085—6090 Hattar S, Liao HW, Takao M, Berson DM, Yau KW 2002 Melanopsin-containing retinal ganglion cells architecture, projections, and intrinsic photosensitivity. Science 295 1065— 1070... 

Hao W and Fong FiK (1999) The endogenous chromophore of retinal G protein-coupled receptor opsin from the pigment epithelium. Journal of Biological Chemistry 274, 6085-90. 

Schadel, SA, Heck, M, Maretzki, D, Filipek, S, Teller, DC, Palczewski, K, and Hofmann, KP, 2003. Ligand channeling within a G-protein-coupled receptor—The entry and exit of retinals in native opsin. J Biol Chem 278, 24896-24903. 

The evidence to-date shows that vertebrate photoreception is mediated by a closely related group of proteins termed opsins. These are G protein-coupled receptors characterized by their ability to bind a vitamin A based chromophore ( -cis-retinal) via a Schiff base linkage using a lysine residue in the 7th transmembrane a helix (Fig. 1). The primary events of image detection by the rods and cones occurs with the absorption of a photon of light by ll-r/r-retinal and its photoisomerization to the AUtrans state (Bums Baylor 2001, Menon et al 2001). Although photoreception is best understood in retinal rods and cones, photoreception is not confined to these structures. In non-mammalian... 

Beyond stmcture determination, soMd-state NMR has been used to investigate the stmctures of membrane bound ligands. Several recent examples are a low-resolution stmcture of neurotensin bound to its G-protein coupled receptor (93), scorpion toxin bound to a chimeric potassium channel (94), retinal in both the rhodopsin and the metarhodopsin II intermediate (95), and acetylchoMne bound to its receptor (96). These studies have great potential for designing and optimizing dmgs-targeting membrane proteins (97). 

M FIGURE 5-13 Structural model of bacteriorhodopsin, a multipass transmembrane protein that functions as a photoreceptor in certain bacteria. The seven hydrophobic a helices in bacteriorhodopsin traverse the lipid bilayer. A retinal molecule (red) covalently attached to one helix absorbs light. The large class of G protein-coupled receptors in eukaryotic cells also has seven membrane-spanning a helices their three-dimensional structure is similar to that of bacteriorhodopsin. [After H. Luecke et al., 1999, J. Mol. Biol. 291 899.]... 

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