2z73
Crystal structure of squid rhodopsin
Structural highlights
FunctionOPSD_TODPA Visual pigments such as rhodopsin and porphyropsin are light-absorbing molecules that mediate vision. Rhodopsin consists of an apoprotein, opsin, covalently linked to 11-cis-retinal. This receptor is coupled to the activation of phospholipase C. Porphyropsin consists of opsin covalently linked to 11-cis 3,4-didehydroretinal. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedInvertebrate phototransduction uses an inositol-1,4,5-trisphosphate signalling cascade in which photoactivated rhodopsin stimulates a G(q)-type G protein, that is, a class of G protein that stimulates membrane-bound phospholipase Cbeta. The same cascade is used by many G-protein-coupled receptors, indicating that invertebrate rhodopsin is a prototypical member. Here we report the crystal structure of squid (Todarodes pacificus) rhodopsin at 2.5 A resolution. Among seven transmembrane alpha-helices, helices V and VI extend into the cytoplasmic medium and, together with two cytoplasmic helices, they form a rigid protrusion from the membrane surface. This peculiar structure, which is not seen in bovine rhodopsin, seems to be crucial for the recognition of G(q)-type G proteins. The retinal Schiff base forms a hydrogen bond to Asn 87 or Tyr 111; it is far from the putative counterion Glu 180. In the crystal, a tight association is formed between the amino-terminal polypeptides of neighbouring monomers; this intermembrane dimerization may be responsible for the organization of hexagonally packed microvillar membranes in the photoreceptor rhabdom. Crystal structure of squid rhodopsin.,Murakami M, Kouyama T Nature. 2008 May 15;453(7193):363-7. PMID:18480818[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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