1. Crystal Structure of Rhodopsin : A G Protein-Coupled Receptor Authors : Krzysztof Palczewski, Takasi Kumasaka, Tetsuya Hori, Craig A. Behnke, Hiroyuki Motoshima, Brian A. Fox, Isolde Le Trong, David C. Teller, Tetsuji Okada, Ronald E. Stenkamp, Masaki Yamamoto, Masashi Miyano Source : VOL 289 4 August 2000 Science Speaker : Ls02 871604 楊又穎

2. G protein : Heterotrimeric guanine nucleotide- binding protein associated with cytoplasmic face of the plasma membrane of mammalian cells, and involved in transmitting signals from receptors to intracellular pathways. Rhodopsin : a G protein-coupled receptor which is conjugated by opsin, phopholipid, retinal. Light sensitive, actived by light turn on the signal pathway that leads to vision.

5. Rhdopsin structure Extracellular region Transmembrane helices Cytoplasmic surface

8. ● Extracellular region -- mutation of Pro23 or Gln28 cause the eye disease retinities pigmentosa ● Transmembrane helices -- Helices H1,4,6,7 are bent at Pro residues -- The location of Gly90 is replaced by Asp causes night blindness (salt-bridge destabilization) -- Some hydrophobic binding sites

9. ● Cytoplasmic surface -- C-IV loop, has a variety of synthesis peptides and their effect on the activation of G protein -- NPXXY motif -- hydrophobic enviroment ● 11 cis-retinal chromophore -- retinylidene group -- trans form

10. ● The crystal structure of rhodopsin reveals a highly organized heptahelical transmembrane bundle with 11-cis-retinal as a key cofactor involved in maintaining rhodopsin in the ground state. ● The structure gives information on the molecular mechanism of GPCR activation. ● A conformational change upon photoactivation of the chromophore that leads to rhodopsin activation and signal transduction. Conclusion