Electrostatic role of the non-heme iron complex in bacterial photosynthetic reaction center

Edited by Peter Brzezinski

Received 17 June 2006; received in revised form 4 July 2006; accepted 7 July 2006. published online 17 July 2006.

Abstract

To elucidate the role of the non-heme iron complex (Fe-complex) in the electron transfer (ET) events of bacterial photosynthetic reaction centers (bRC), we calculated redox potentials of primary/secondary quinones QA/B (Em(QA/B)) in the Fe-depleted bRC. Removing the Fe-complex, the calculated Em(QA/B) are downshifted by ∼220mV/∼80mV explaining both the 15-fold decrease in ET rate from bacteriopheophytin to QA and triplet state occurrence in Fe-depleted bRC. The larger downshift in Em(QA) relative to Em(QB) increases the driving-energy for ET from QA to QB by 140meV, in agreement with ∼100meV increase derived from kinetic studies.

Keywords: Non-heme iron, Redox potential, Quinone, Electron transfer, Bacterial photosynthetic reaction center, Photosystem II

Institute of Chemistry and Biochemistry, Free University of Berlin, Takustrasse 6, D-14195 Berlin, Germany

Corresponding author. Fax: +49 30 83856921.

1 Present address: Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, USA.

PII: S0014-5793(06)00858-1

doi:10.1016/j.febslet.2006.07.023

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