Crystal Structure of Squid Rhodopsin with Intracellularly Extended Cytoplasmic Region

G-protein-coupled receptors play a key step in cellular signal transduction cascades by transducing various extracellular signals via G-proteins. Rhodopsin is a prototypical G-protein-coupled receptor involved in the retinal visual signaling cascade. We determined the structure of squid rhodopsin at...

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Published in:The Journal of biological chemistry 2008-06, Vol.283 (26), p.17753-17756
Main Authors: Shimamura, Tatsuro, Hiraki, Kenji, Takahashi, Naoko, Hori, Tetsuya, Ago, Hideo, Masuda, Katsuyoshi, Takio, Koji, Ishiguro, Masaji, Miyano, Masashi
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Cattle
Crystallography, X-Ray - methods
Cytoplasm - metabolism
Decapodiformes
Hydrogen Bonding
Marine
Molecular Sequence Data
Protein Conformation
Protein Structure, Secondary
Protein Structure, Tertiary
Receptors, Adrenergic, beta-2 - chemistry
Receptors, G-Protein-Coupled - metabolism
Rhodopsin - chemistry
Sequence Homology, Amino Acid
Teuthida
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Summary:G-protein-coupled receptors play a key step in cellular signal transduction cascades by transducing various extracellular signals via G-proteins. Rhodopsin is a prototypical G-protein-coupled receptor involved in the retinal visual signaling cascade. We determined the structure of squid rhodopsin at 3.7Å resolution, which transduces signals through the Gq protein to the phosphoinositol cascade. The structure showed seven transmembrane helices and an amphipathic helix H8 has similar geometry to structures from bovine rhodopsin, coupling to Gt, and humanβ2-adrenergic receptor, coupling to Gs. Notably, squid rhodopsin contains a well structured cytoplasmic region involved in the interaction with G-proteins, and this region is flexible or disordered in bovine rhodopsin and humanβ2-adrenergic receptor. The transmembrane helices 5 and 6 are longer and extrude into the cytoplasm. The distal C-terminal tail contains a short hydrophilic α-helix CH after the palmitoylated cysteine residues. The residues in the distal C-terminal tail interact with the neighboring residues in the second cytoplasmic loop, the extruded transmembrane helices 5 and 6, and the short helix H8. Additionally, the Tyr-111, Asn-87, and Asn-185 residues are located within hydrogen-bonding distances from the nitrogen atom of the Schiff base.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.C800040200