title: Crystal structure of opsin in its G-protein-interacting conformation.
abstract: Opsin, the ligand-free form of the G-protein-coupled receptor rhodopsin, at low pH adopts a conformationally distinct, active G-protein-binding state known as Ops*. A synthetic peptide derived from the main binding site of the heterotrimeric G protein-the carboxy terminus of the alpha-subunit (GalphaCT)-stabilizes Ops*. Here we present the 3.2 A crystal structure of the bovine Ops*-GalphaCT peptide complex. GalphaCT binds to a site in opsin that is opened by an outward tilt of transmembrane helix (TM) 6, a pairing of TM5 and TM6, and a restructured TM7-helix 8 kink. Contacts along the inner surface of TM5 and TM6 induce an alpha-helical conformation in GalphaCT with a C-terminal reverse turn. Main-chain carbonyl groups in the reverse turn constitute the centre of a hydrogen-bonded network, which links the two receptor regions containing the conserved E(D)RY and NPxxY(x)(5,6)F motifs. On the basis of the Ops*-GalphaCT structure and known conformational changes in Galpha, we discuss signal transfer from the receptor to the G protein nucleotide-binding site.
authors.affiliation: Institut für Medizinische Physik und Biophysik (CC2), Charité - Universitätsmedizin Berlin, Charitéplatz 1, D-10117 Berlin, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Scheerer
authors.forename: Jung Hee
authors.initials: JH
authors.lastname: Park
authors.forename: Peter W
authors.initials: PW
authors.lastname: Hildebrand
authors.forename: Yong Ju
authors.initials: YJ
authors.lastname: Kim
authors.forename: Norbert
authors.initials: N
authors.lastname: Krauss
authors.forename: Hui-Woog
authors.initials: HW
authors.lastname: Choe
authors.forename: Klaus Peter
authors.initials: KP
authors.lastname: Hofmann
authors.forename: Oliver P
authors.initials: OP
authors.lastname: Ernst
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001120:Arginine / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002417:Cattle; D017124:Conserved Sequence; D003460:Crystallization; D018360:Crystallography, X-Ray; D044385:GTP-Binding Protein alpha Subunits / Q000737:chemistry* / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D011487:Protein Conformation; D012038:Regeneration; D012172:Retinaldehyde / Q000737:chemistry / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry; D017299:Rod Opsins / Q000737:chemistry* / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D044385:GTP-Binding Protein alpha Subunits; D017299:Rod Opsins; D012243:Rhodopsin; D001120:Arginine; D012172:Retinaldehyde