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Title: Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering

Abstract

Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision under dim light conditions. During rhodopsin photoactivation, the chromophore retinal undergoes cis-trans isomerization, and subsequently dissociates from the protein yielding the opsin apoprotein [1]. What are the changes in protein dynamics that occur during the rhodopsin photoactivation process? Here, we studied the microscopic dynamics of the dark-state rhodopsin and the ligand-free opsin using quasi-elastic neutron scattering (QENS). The QENS technique tracks the individual hydrogen atom motions in the protein molecules, because the neutron scattering cross-section of hydrogen is much higher than other atoms [2-4]. We used protein (rhodopsin/opsin) samples with CHAPS detergent hydrated with heavy water. The solvent signal is suppressed due to the heavy water, so that only the signals from proteins and detergents are detected. The activation of proteins is confirmed at low temperatures up to 300 K by the mean-square displacement (MSD) analysis. Our QENS experiments conducted at temperatures ranging from 220 K to 300 K clearly indicate that the protein dynamic behavior increases with temperature. The relaxation time for the ligand-bound protein rhodopsin was longer compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanyingmore » CHAPS detergent, which forms a band around the protein molecule in the micelle. Unlike the protein, the CHAPS detergent manifests localized motions that are the same as in the bulk empty micelles. Furthermore QENS provides unique understanding of the key dynamics involved in the activation of the GPCR involved in the visual process.« less

Authors:
 [1];  [1];  [2];  [2];  [3];  [2];  [1]
  1. Wayne State Univ., Detroit, MI (United States)
  2. Univ. of Arizona, Tucson, AZ (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org.:
USDOE
OSTI Identifier:
1329127
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Biophysical Journal
Additional Journal Information:
Journal Volume: 108; Journal Issue: S1; Journal ID: ISSN 0006-3495
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Bhowmik, Debsindhu, Shrestha, Utsab, Perera, Suchithranga M.d.c., Chawla, Udeep, Mamontov, Eugene, Brown, Michael F., and Chu, Xiang -Qiang. Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering. United States: N. p., 2015. Web. doi:10.1016/j.bpj.2014.11.366.
Bhowmik, Debsindhu, Shrestha, Utsab, Perera, Suchithranga M.d.c., Chawla, Udeep, Mamontov, Eugene, Brown, Michael F., & Chu, Xiang -Qiang. Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering. United States. doi:10.1016/j.bpj.2014.11.366.
Bhowmik, Debsindhu, Shrestha, Utsab, Perera, Suchithranga M.d.c., Chawla, Udeep, Mamontov, Eugene, Brown, Michael F., and Chu, Xiang -Qiang. Tue . "Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering". United States. doi:10.1016/j.bpj.2014.11.366. https://www.osti.gov/servlets/purl/1329127.
@article{osti_1329127,
title = {Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering},
author = {Bhowmik, Debsindhu and Shrestha, Utsab and Perera, Suchithranga M.d.c. and Chawla, Udeep and Mamontov, Eugene and Brown, Michael F. and Chu, Xiang -Qiang},
abstractNote = {Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision under dim light conditions. During rhodopsin photoactivation, the chromophore retinal undergoes cis-trans isomerization, and subsequently dissociates from the protein yielding the opsin apoprotein [1]. What are the changes in protein dynamics that occur during the rhodopsin photoactivation process? Here, we studied the microscopic dynamics of the dark-state rhodopsin and the ligand-free opsin using quasi-elastic neutron scattering (QENS). The QENS technique tracks the individual hydrogen atom motions in the protein molecules, because the neutron scattering cross-section of hydrogen is much higher than other atoms [2-4]. We used protein (rhodopsin/opsin) samples with CHAPS detergent hydrated with heavy water. The solvent signal is suppressed due to the heavy water, so that only the signals from proteins and detergents are detected. The activation of proteins is confirmed at low temperatures up to 300 K by the mean-square displacement (MSD) analysis. Our QENS experiments conducted at temperatures ranging from 220 K to 300 K clearly indicate that the protein dynamic behavior increases with temperature. The relaxation time for the ligand-bound protein rhodopsin was longer compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which forms a band around the protein molecule in the micelle. Unlike the protein, the CHAPS detergent manifests localized motions that are the same as in the bulk empty micelles. Furthermore QENS provides unique understanding of the key dynamics involved in the activation of the GPCR involved in the visual process.},
doi = {10.1016/j.bpj.2014.11.366},
journal = {Biophysical Journal},
number = S1,
volume = 108,
place = {United States},
year = {Tue Jan 27 00:00:00 EST 2015},
month = {Tue Jan 27 00:00:00 EST 2015}
}

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