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PDBsum entry 2hpy
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Signaling protein
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PDB id
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2hpy
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References listed in PDB file
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Key reference
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Title
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Local peptide movement in the photoreaction intermediate of rhodopsin.
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Authors
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H.Nakamichi,
T.Okada.
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Ref.
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Proc Natl Acad Sci U S A, 2006,
103,
12729-12734.
[DOI no: ]
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PubMed id
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Abstract
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Photoactivation of the visual rhodopsin, a prototypical G protein-coupled
receptor (GPCR), involves efficient conversion of the intrinsic inverse-agonist
11-cis-retinal to the all-trans agonist. This event leads to the rearrangement
of the heptahelical transmembrane bundle, which is thought to be shared by
hundreds of GPCRs. To examine this activation mechanism, we determined the x-ray
crystallographic model of the photoreaction intermediate of rhodopsin,
lumirhodopsin, which represents the conformational state having the nearly
complete all-trans agonist form of the retinal. A difference electron density
map clearly indicated that the distorted all-trans-retinal in the precedent
intermediate bathorhodopsin relaxes by dislocation of the beta-ionone ring in
lumirhodopsin, along with significant peptide displacement in the middle of
helix III, including approximately two helical turns. This local movement
results in the breaking of the electrostatic interhelical restraints mediated by
many of the conserved residues among rhodopsin-like GPCRs, with consequent
acquisition of full activity.
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Figure 3.
Fig. 3. Differences between RHO and LUMI. (A–C)
Projection views of the three regions containing the difference
electron densities between RHO and LUMI. Each image is a
10-Å slab section from the extracellular (A) to
cytoplasmic (C) side of the transmembrane helical domain.
Positive (blue) and negative (red) electron densities contoured
to 3.5  level are shown on the
 -carbon traces of the
seven helices. (D) Superposition of the crystallographic models
of RHO (green) and LUMI (orange). Only the -carbon traces and the
retinal chromophore are shown.
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Figure 4.
Fig. 4. Crystallographic models of the three states of RHO.
(A) Projection view around the retinal with some amino acid
residues. Shown are the three models: RHO (green), BATHO (red),
and LUMI (orange). (B) Structural changes between RHO (green)
and LUMI (orange) around the middle of helix III. The four bound
water molecules in this site are shown as small light blue
spheres, which are fixed in the positions found in the
ground-state structure.
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