Sequential Rearrangement of Interhelical Networks Upon Rhodopsin Activation in Membranes: The Meta IIa Conformational Substate
- 15 March 2010
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 132 (13), 4815-4821
- https://doi.org/10.1021/ja910317a
Abstract
Photon absorption by rhodopsin is proposed to lead to an activation pathway that is described by the extended reaction scheme Meta I ⇌ Meta IIa ⇌ Meta IIb ⇌ Meta IIbH+, where Meta IIbH+ is thought to be the conformational substate that activates the G protein transducin. Here we test this extended scheme for rhodopsin in a membrane bilayer environment by investigating lipid perturbation of the activation mechanism. We found that symmetric membrane lipids having two unsaturated acyl chains, such as 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), selectively stabilize the Meta IIa substate in the above mechanism. By combining FTIR and UV−visible difference spectroscopy, we characterized the structural and functional changes involved in the transition to the Meta IIa intermediate, which links the inactive Meta I intermediate with the Meta IIb states formed by helix rearrangement. Besides the opening of the Schiff base ionic lock, the Meta IIa substate is characterized by an activation switch in a conserved water-mediated hydrogen-bonded network involving transmembrane helices H1/H2/H7, which is sensed by its key residue Asp83. On the other hand, movement of retinal toward H5 and its interaction with another interhelical H3/H5 network mediated by His211 and Glu122 is absent in Meta IIa. The latter rearrangement takes place only in the subsequent transition to Meta IIb, which has been previously associated with movement of H6. Our results imply that activating structural changes in the H1/H2/H7 network are triggered by disruption of the Schiff base salt bridge and occur prior to other chromophore-induced changes in the H3/H5 network and the outward tilt of H6 in the activation process.Keywords
This publication has 50 references indexed in Scilit:
- Light Activation of Rhodopsin: Insights from Molecular Dynamics Simulations Guided by Solid-State NMR Distance RestraintsJournal of Molecular Biology, 2010
- Multiple Switches in G Protein-Coupled Receptor ActivationTrends in Pharmacological Sciences, 2009
- Helix movement is coupled to displacement of the second extracellular loop in rhodopsin activationNature Structural & Molecular Biology, 2009
- Two protonation switches control rhodopsin activation in membranesProceedings of the National Academy of Sciences of the United States of America, 2008
- A moving story of receptorsNature, 2008
- Distinct conformational changes in β-arrestin report biased agonism at seven-transmembrane receptorsProceedings of the National Academy of Sciences of the United States of America, 2008
- Sequence of late molecular events in the activation of rhodopsinProceedings of the National Academy of Sciences of the United States of America, 2007
- Local peptide movement in the photoreaction intermediate of rhodopsinProceedings of the National Academy of Sciences of the United States of America, 2006
- Crystallographic Analysis of Primary Visual PhotochemistryAngewandte Chemie-International Edition, 2006
- Conformational States and Dynamics of Rhodopsin in Micelles and BilayersBiochemistry, 2006