Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 7-Day Trial for You or Your Team.

Learn More →

Voltage changes involving photosystem II quinone–iron complex turnover

Voltage changes involving photosystem II quinone–iron complex turnover An electrometrical technique was used to investigate proton-coupled electron transfer between the primary plastoquinone acceptor Q A − and the oxidized non-heme iron Fe3+ on the acceptor side of photosystem II core particles incorporated into phospholipid vesicles. The sign of the transmembrane electric potential difference Δψ (negative charging of the proteoliposome interior) indicates that the iron–quinone complex faces the interior surface of the proteoliposome membrane. Preoxidation of the non-heme iron was achieved by addition of potassium ferricyanide entrapped into proteoliposomes. Besides the fast unresolvable kinetic phase (τ ∼ 0.1 μs) of Δψ generation related to electron transfer between the redox-active tyrosine YZ and QA, an additional phase in the submillisecond time domain (τ ∼ 0.1 ms at 23°C, pH 7.0) and relative amplitude ∼ 20% of the amplitude of the fast phase was observed under exposure to the first flash. This phase was absent under the second laser flash, as well as upon the first flash in the presence of DCMU, an inhibitor of electron transfer between QA and the secondary quinone QB. The rate of the additional electrogenic phase is decreased by about one-half in the presence of D2O and is reduced with the temperature decrease. On the basis of the above observations we suggest that the submillisecond electrogenic reaction induced by the first flash is due to the vectorial transfer of a proton from external aqueous phase to an amino acid residue(s) in the vicinity of the non-heme iron. The possible role of the non-heme iron in cyclic electron transfer in photosystem II complex is discussed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png European Biophysics Journal Springer Journals

Voltage changes involving photosystem II quinone–iron complex turnover

Download PDF
8 pages

Loading next page...
 
/lp/springer-journals/voltage-changes-involving-photosystem-ii-quinone-iron-complex-turnover-URkGok2Cc0

References (55)

Publisher
Springer Journals
Copyright
Copyright © 2006 by EBSA
Subject
Life Sciences; Biochemistry, general; Biological and Medical Physics, Biophysics; Cell Biology; Neurobiology; Membrane Biology; Nanotechnology
ISSN
0175-7571
eISSN
1432-1017
DOI
10.1007/s00249-006-0069-3
pmid
16708211
Publisher site
See Article on Publisher Site

Abstract

An electrometrical technique was used to investigate proton-coupled electron transfer between the primary plastoquinone acceptor Q A − and the oxidized non-heme iron Fe3+ on the acceptor side of photosystem II core particles incorporated into phospholipid vesicles. The sign of the transmembrane electric potential difference Δψ (negative charging of the proteoliposome interior) indicates that the iron–quinone complex faces the interior surface of the proteoliposome membrane. Preoxidation of the non-heme iron was achieved by addition of potassium ferricyanide entrapped into proteoliposomes. Besides the fast unresolvable kinetic phase (τ ∼ 0.1 μs) of Δψ generation related to electron transfer between the redox-active tyrosine YZ and QA, an additional phase in the submillisecond time domain (τ ∼ 0.1 ms at 23°C, pH 7.0) and relative amplitude ∼ 20% of the amplitude of the fast phase was observed under exposure to the first flash. This phase was absent under the second laser flash, as well as upon the first flash in the presence of DCMU, an inhibitor of electron transfer between QA and the secondary quinone QB. The rate of the additional electrogenic phase is decreased by about one-half in the presence of D2O and is reduced with the temperature decrease. On the basis of the above observations we suggest that the submillisecond electrogenic reaction induced by the first flash is due to the vectorial transfer of a proton from external aqueous phase to an amino acid residue(s) in the vicinity of the non-heme iron. The possible role of the non-heme iron in cyclic electron transfer in photosystem II complex is discussed.

Journal

European Biophysics Journal – Springer Journals

Published: May 18, 2006

There are no references for this article.