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Towards an interpretation of 13C chemical shifts in bathorhodopsin, a functional intermediate of a G-protein coupled receptor

Towards an interpretation of 13C chemical shifts in bathorhodopsin, a functional intermediate of a G-protein coupled receptor
Towards an interpretation of 13C chemical shifts in bathorhodopsin, a functional intermediate of a G-protein coupled receptor
Photoisomerization of the membrane-bound light receptor protein rhodopsin leads to an energy-rich photostate called bathorhodopsin, which may be trapped at temperatures of 120 K or lower. We recently studied bathorhodopsin by low-temperature solid-state NMR, using in situ illumination of the sample in a purpose-built NMR probe. In this way we acquired 13C chemical shifts along the retinylidene chain of the chromophore. Here we compare these results with the chemical shifts of the dark state chromophore in rhodopsin, as well as with the chemical shifts of retinylidene model compounds in solution. An earlier solid-state NMR study of bathorhodopsin found only small changes in the 13C chemical shifts upon isomerization, suggesting only minor perturbations of the electronic structure in the isomerized retinylidene chain. This is at variance with our recent measurements which show much larger perturbations of the 13C chemical shifts. Here we present a tentative interpretation of our NMR results involving an increased charge delocalization inside the polyene chain of the bathorhodopsin chromophore. Our results suggest that the bathochromic shift of bathorhodopsin is due to modified electrostatic interactions between the chromophore and the binding pocket, whereas both electrostatic interactions and torsional strain are involved in the energy storage mechanism of bathorhodopsin.

double-quantum solid-state nmr, bathorhodopsin, retinylidene psb, 13c chemical shift, energy storage, bathochromic shift
0304-4165
1350-1357
Gansmüller, Axel
67c127f1-7776-436e-b195-5e137c47fbce
Concistrè, Maria
4d926227-2c26-489b-ac6c-ccc1354c68db
McLean, Neville
49721be3-0ab4-409a-bf6d-eacdfc3848fa
Johannessen, Ole G.
799ccc8c-a2e7-4305-a03a-2dc9f42564ef
Marín-Montesinos, Ildefonso
17e30907-11ac-49a9-9032-0eaa46ac2c2e
Bovee-Geurts, Petra H.M.
66d6099e-73b5-4f84-ae7a-2b61d874e4e9
Verdegem, Peter
eb03ab19-3b7b-4dc0-a9fd-015580faa1d3
Lugtenburg, Johan
b920f5ab-0138-479f-88b1-f4bca6b32dad
Brown, Richard C.D.
21ce697a-7c3a-480e-919f-429a3d8550f5
DeGrip, Willem J.
3fe658dc-e4cd-4d05-9771-417fd462ae72
Malcolm H., Levitt
00c887c0-5431-4b09-a016-ad677bf89e89
Gansmüller, Axel
67c127f1-7776-436e-b195-5e137c47fbce
Concistrè, Maria
4d926227-2c26-489b-ac6c-ccc1354c68db
McLean, Neville
49721be3-0ab4-409a-bf6d-eacdfc3848fa
Johannessen, Ole G.
799ccc8c-a2e7-4305-a03a-2dc9f42564ef
Marín-Montesinos, Ildefonso
17e30907-11ac-49a9-9032-0eaa46ac2c2e
Bovee-Geurts, Petra H.M.
66d6099e-73b5-4f84-ae7a-2b61d874e4e9
Verdegem, Peter
eb03ab19-3b7b-4dc0-a9fd-015580faa1d3
Lugtenburg, Johan
b920f5ab-0138-479f-88b1-f4bca6b32dad
Brown, Richard C.D.
21ce697a-7c3a-480e-919f-429a3d8550f5
DeGrip, Willem J.
3fe658dc-e4cd-4d05-9771-417fd462ae72
Malcolm H., Levitt
00c887c0-5431-4b09-a016-ad677bf89e89

Gansmüller, Axel, Concistrè, Maria, McLean, Neville, Johannessen, Ole G., Marín-Montesinos, Ildefonso, Bovee-Geurts, Petra H.M., Verdegem, Peter, Lugtenburg, Johan, Brown, Richard C.D., DeGrip, Willem J. and Malcolm H., Levitt (2009) Towards an interpretation of 13C chemical shifts in bathorhodopsin, a functional intermediate of a G-protein coupled receptor. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1788 (6), 1350-1357. (doi:10.1016/j.bbamem.2009.02.018). (PMID:19265671)

Record type: Article

Abstract

Photoisomerization of the membrane-bound light receptor protein rhodopsin leads to an energy-rich photostate called bathorhodopsin, which may be trapped at temperatures of 120 K or lower. We recently studied bathorhodopsin by low-temperature solid-state NMR, using in situ illumination of the sample in a purpose-built NMR probe. In this way we acquired 13C chemical shifts along the retinylidene chain of the chromophore. Here we compare these results with the chemical shifts of the dark state chromophore in rhodopsin, as well as with the chemical shifts of retinylidene model compounds in solution. An earlier solid-state NMR study of bathorhodopsin found only small changes in the 13C chemical shifts upon isomerization, suggesting only minor perturbations of the electronic structure in the isomerized retinylidene chain. This is at variance with our recent measurements which show much larger perturbations of the 13C chemical shifts. Here we present a tentative interpretation of our NMR results involving an increased charge delocalization inside the polyene chain of the bathorhodopsin chromophore. Our results suggest that the bathochromic shift of bathorhodopsin is due to modified electrostatic interactions between the chromophore and the binding pocket, whereas both electrostatic interactions and torsional strain are involved in the energy storage mechanism of bathorhodopsin.

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More information

Published date: June 2009
Keywords: double-quantum solid-state nmr, bathorhodopsin, retinylidene psb, 13c chemical shift, energy storage, bathochromic shift

Identifiers

Local EPrints ID: 178391
URI: http://eprints.soton.ac.uk/id/eprint/178391
ISSN: 0304-4165
PURE UUID: cb8c3c90-e25e-4a9f-a27a-1a705c583f71
ORCID for Richard C.D. Brown: ORCID iD orcid.org/0000-0003-0156-7087

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Date deposited: 24 Mar 2011 14:53
Last modified: 10 Dec 2019 01:53

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Contributors

Author: Axel Gansmüller
Author: Maria Concistrè
Author: Neville McLean
Author: Ole G. Johannessen
Author: Ildefonso Marín-Montesinos
Author: Petra H.M. Bovee-Geurts
Author: Peter Verdegem
Author: Johan Lugtenburg
Author: Willem J. DeGrip
Author: Levitt Malcolm H.

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