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PDBsum entry 3cap
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Signaling protein
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PDB id
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3cap
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References listed in PDB file
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Key reference
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Title
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Crystal structure of the ligand-Free g-Protein-Coupled receptor opsin.
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Authors
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J.H.Park,
P.Scheerer,
K.P.Hofmann,
H.W.Choe,
O.P.Ernst.
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Ref.
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Nature, 2008,
454,
183-187.
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PubMed id
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Abstract
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In the G-protein-coupled receptor (GPCR) rhodopsin, the inactivating ligand
11-cis-retinal is bound in the seven-transmembrane helix (TM) bundle and is
cis/trans isomerized by light to form active metarhodopsin II. With
metarhodopsin II decay, all-trans-retinal is released, and opsin is reloaded
with new 11-cis-retinal. Here we present the crystal structure of ligand-free
native opsin from bovine retinal rod cells at 2.9 ångström (A) resolution.
Compared to rhodopsin, opsin shows prominent structural changes in the conserved
E(D)RY and NPxxY(x)(5,6)F regions and in TM5-TM7. At the cytoplasmic side, TM6
is tilted outwards by 6-7 A, whereas the helix structure of TM5 is more
elongated and close to TM6. These structural changes, some of which were
attributed to an active GPCR state, reorganize the empty retinal-binding pocket
to disclose two openings that may serve the entry and exit of retinal. The opsin
structure sheds new light on ligand binding to GPCRs and on GPCR activation.
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