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Helix movement is coupled to displacement of the second extracellular loop in rhodopsin activation

Ahuja, S and Hornak, V and Yan, ECY and Syrett, N and Goncalves, JA and Hirshfeld, A and Ziliox, M and Sakmar, TP and Sheves, M and Reeves, PJ and Smith, SO and Eilers, M (2009) 'Helix movement is coupled to displacement of the second extracellular loop in rhodopsin activation.' Nature Structural and Molecular Biology, 16 (2). 168 - 175. ISSN 1545-9993

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The second extracellular loop (EL2) of rhodopsin forms a cap over the binding site of its photoreactive 11-cis retinylidene chromophore. A crucial question has been whether EL2 forms a reversible gate that opens upon activation or acts as a rigid barrier. Distance measurements using solid-state 13C NMR spectroscopy between the retinal chromophore and the β4 strand of EL2 show that the loop is displaced from the retinal binding site upon activation, and there is a rearrangement in the hydrogen-bonding networks connecting EL2 with the extracellular ends of transmembrane helices H4, H5 and H6. NMR measurements further reveal that structural changes in EL2 are coupled to the motion of helix H5 and breaking of the ionic lock that regulates activation. These results provide a comprehensive view of how retinal isomerization triggers helix motion and activation in this prototypical G protein-coupled receptor. © 2009 Nature America, Inc. All rights reserved.

Item Type: Article
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health > Life Sciences, School of
Depositing User: Jim Jamieson
Date Deposited: 07 Oct 2011 14:13
Last Modified: 26 Aug 2019 08:15

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