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Title: Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides

Ubiquinone forms an integral part of the electron transport chain in cellular respiration and photosynthesis across a vast number of organisms. Prior experimental results have shown that the photosynthetic reaction center (RC) from Rhodobacter sphaeroides is only fully functional with a limited set of methoxy-bearing quinones, suggesting that specific interactions with this substituent are required to drive electron transport and the formation of quinol. The nature of these interactions has yet to be determined. Through parameterization of a CHARMM-compatible quinone force field and subsequent molecular dynamics simulations of the quinone-bound RC, in this paper we have investigated and characterized the interactions of the protein with the quinones in the Q A and Q B sites using both equilibrium simulation and thermodynamic integration. In particular, we identify a specific interaction between the 2-methoxy group of ubiquinone in the Q B site and the amide nitrogen of GlyL225 that we implicate in locking the orientation of the 2-methoxy group, thereby tuning the redox potential difference between the quinones occupying the Q A and Q B sites. Finally, disruption of this interaction leads to weaker binding in a ubiquinone analogue that lacks a 2-methoxy group, a finding supported by reverse electron transfer electronmore » paramagnetic resonance experiments of the Q A–Q B– biradical and competitive binding assays.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States)
Publication Date:
Grant/Contract Number:
FG02-97ER25308; FG02-08ER15960; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Biochemistry
Additional Journal Information:
Journal Volume: 54; Journal Issue: 12; Journal ID: ISSN 0006-2960
Publisher:
American Chemical Society (ACS)
Research Org:
Univ. of Illinois at Urbana-Champaign, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1344901

Vermaas, Josh V., Taguchi, Alexander T., Dikanov, Sergei A., Wraight, Colin A., and Tajkhorshid, Emad. Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides. United States: N. p., Web. doi:10.1021/acs.biochem.5b00033.
Vermaas, Josh V., Taguchi, Alexander T., Dikanov, Sergei A., Wraight, Colin A., & Tajkhorshid, Emad. Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides. United States. doi:10.1021/acs.biochem.5b00033.
Vermaas, Josh V., Taguchi, Alexander T., Dikanov, Sergei A., Wraight, Colin A., and Tajkhorshid, Emad. 2015. "Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides". United States. doi:10.1021/acs.biochem.5b00033. https://www.osti.gov/servlets/purl/1344901.
@article{osti_1344901,
title = {Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides},
author = {Vermaas, Josh V. and Taguchi, Alexander T. and Dikanov, Sergei A. and Wraight, Colin A. and Tajkhorshid, Emad},
abstractNote = {Ubiquinone forms an integral part of the electron transport chain in cellular respiration and photosynthesis across a vast number of organisms. Prior experimental results have shown that the photosynthetic reaction center (RC) from Rhodobacter sphaeroides is only fully functional with a limited set of methoxy-bearing quinones, suggesting that specific interactions with this substituent are required to drive electron transport and the formation of quinol. The nature of these interactions has yet to be determined. Through parameterization of a CHARMM-compatible quinone force field and subsequent molecular dynamics simulations of the quinone-bound RC, in this paper we have investigated and characterized the interactions of the protein with the quinones in the QA and QB sites using both equilibrium simulation and thermodynamic integration. In particular, we identify a specific interaction between the 2-methoxy group of ubiquinone in the QB site and the amide nitrogen of GlyL225 that we implicate in locking the orientation of the 2-methoxy group, thereby tuning the redox potential difference between the quinones occupying the QA and QB sites. Finally, disruption of this interaction leads to weaker binding in a ubiquinone analogue that lacks a 2-methoxy group, a finding supported by reverse electron transfer electron paramagnetic resonance experiments of the QA–QB– biradical and competitive binding assays.},
doi = {10.1021/acs.biochem.5b00033},
journal = {Biochemistry},
number = 12,
volume = 54,
place = {United States},
year = {2015},
month = {3}
}