Publication Date:
2008-05-16
Description:
Invertebrate 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Murakami, Midori -- Kouyama, Tsutomu -- England -- Nature. 2008 May 15;453(7193):363-7. doi: 10.1038/nature06925.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18480818" target="_blank"〉PubMed〈/a〉
Keywords:
Amino Acid Sequence
;
Animals
;
Crystallography, X-Ray
;
Decapodiformes/*chemistry
;
Dimerization
;
Models, Molecular
;
Molecular Sequence Data
;
Protein Structure, Secondary
;
Retinaldehyde/metabolism
;
Rhodopsin/*chemistry/metabolism
;
Schiff Bases
;
Vision, Ocular/physiology
;
Water/chemistry/metabolism
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
