Imperial College London
Alternate

Professor Bill Rutherford FRS

Faculty of Natural Sciences, Department of Life Sciences

Chair in Biochemistry of Solar Energy
 
 
 
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Contact

 

+44 (0)20 7594 5329a.rutherford Website

 
 
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Location

 

702Sir Ernst Chain BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{De:2019:10.1073/pnas.1910675116,
author = {De, Causmaecker S and Douglass, J and Fantuzzi, A and Nitschke, W and Rutherford, A},
doi = {10.1073/pnas.1910675116},
journal = {Proceedings of the National Academy of Sciences of USA},
pages = {19458--19463},
title = {Energetics of the exchangeable quinone, QB, in Photosystem II},
url = {http://dx.doi.org/10.1073/pnas.1910675116},
volume = {116},
year = {2019}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Photosystem II (PSII), the light-driven water/plastoquinone photo-oxidoreductase, is of central importance  in  the  planetary  energy  cycle.  The  product  of  the  reaction,  plastohydroquinone  (PQH2), is released into the membrane from the QB-site, where it is formed. A plastoquinone  (PQ) from the membrane pool then binds into the QB-site. Despite their functional importance, the thermodynamic properties of the PQ in the QB-site, QB,  in its different redox forms have  received relatively little attention. Here we report the midpoint potentials (Em) of QB in PSII from Thermosynechococcus  elongatus  using  EPR  spectroscopy:  Em QB/QB•−≈  90 mV  and  Em QB•−/QBH2≈ 40 mV.  These data allow the following conclusions: 1) the semiquinone, QB•−, is stabilized thermodynamically;  2) the resulting  Em  QB/QBH2  (~    65 mV)  is  lower  than  the EmPQ/PQH2  (~117 mV),  and the difference  (ΔE ~50 meV)  represents  the  driving  force  for QBH2 release into the pool; 3) PQ is ~ 50x more tightly bound than PQH2; 4) the difference between the Em QB/QB•− measured here and the Em QA/QA•− from the literature is ~234 meV,  in  principle  corresponding  to  the  driving  force  for  electron  transfer  from  QA•−  to  QB.   The pH-dependence of the thermoluminescence associated with QB•− provided   a functional estimate for this energy gap and gave a similar value (≥180 meV). These estimates are larger than the generally  accepted  value  (~70 meV)  and  this  is  discussed.  The  energetics  of  QB  in  PSII  are comparable to those in the homologous purple bacterial reaction center.
AU  - De,Causmaecker S
AU  - Douglass,J
AU  - Fantuzzi,A
AU  - Nitschke,W
AU  - Rutherford,A
DO  - 10.1073/pnas.1910675116
EP  - 19463
PY  - 2019///
SN  - 0027-8424
SP  - 19458
TI  - Energetics of the exchangeable quinone, QB, in Photosystem II
T2  - Proceedings of the National Academy of Sciences of USA
UR  - http://dx.doi.org/10.1073/pnas.1910675116
UR  - http://hdl.handle.net/10044/1/73131
VL  - 116
ER  -
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