help button home button Biophys. J.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Shinkarev, V. P.
Right arrow Articles by Golbeck, J. H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Shinkarev, V. P.
Right arrow Articles by Golbeck, J. H.

Biophys J, December 2002, p. 2885-2897, Vol. 83, No. 6

Modeling of the P700+ Charge Recombination Kinetics with Phylloquinone and Plastoquinone-9 in the A1 Site of Photosystem I

Vladimir P. Shinkarev,* Boris Zybailov,dagger Ilya R. Vassiliev,dagger and John H. Golbeckdagger

 *Department of Biochemistry, University of Illinois, Urbana, Illinois 61801, and  dagger Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 USA

Light activation of photosystem I (PS I) induces electron transfer from the excited primary electron donor P700 (a special pair of chlorophyll a/a' molecules) to three iron-sulfur clusters, FX, FA, and FB via acceptors A0 (a monomeric chlorophyll a) and A1 (phylloquinone). PS I complexes isolated from menA and menB mutants contain plastoquinone-9 rather than phylloquinone in the A1 site and show altered rates of forward electron transfer from A<UP><SUB>1</SUB><SUP>−</SUP></UP> to [FA/FB] and altered rates of back electron transfer from [FA/FB]- to P700+ (Semenov, A. Y., et al., J. Biol. Chem. 275:23429-23438, 2000). To identify the modified electron transfer steps, we studied the kinetics of flash-induced P700+ reduction in PS I that contains either an intact set or a subset of iron-sulfur clusters FX, FA, and FB and with the A1 binding site occupied by phylloquinone or plastoquinone-9. A modeling of the forward and backward electron transfer kinetics in P700-FA/FB complexes, P700-FX cores, and P700-A1 cores shows that the replacement of phylloquinone by plastoquinone-9 induces a decrease in the free energy gap between A1 and FA/FB from ~-205 mV in wild-type PS I to ~-70 mV in menA PS I. The +135 mV increase in the midpoint potential of A1 explains the acceleration in the rate of P700+ dark reduction in menA PS I, and the resulting uphill electron transfer from A1 to FX in menA PS I explains the absence of a contribution from F<UP><SUB>X</SUB><SUP>−</SUP></UP> to the reduction of P700+. This fully quantitative description of PS I relates electron transfer rates, equilibrium constants, and redox potentials, and can be used to predict changes in these parameters upon substitution of electron transfer cofactors.

Biophys J, December 2002, p. 2885-2897, Vol. 83, No. 6
© 2002 by the Biophysical Society   0006-3495/02/12/2885/13  $2.00


This article has been cited by other articles:


Home page
 J. Biol. Chem.Home page
Y. Sakuragi, B. Zybailov, G. Shen, D. A. Bryant, J. H. Golbeck, B. A. Diner, I. Karygina, Y. Pushkar, and D. Stehlik
Recruitment of a Foreign Quinone into the A1 Site of Photosystem I: CHARACTERIZATION OF A menB rubA DOUBLE DELETION MUTANT IN SYNECHOCOCCUS SP. PCC 7002 DEVOID OF FX, FA, AND FB AND CONTAINING PLASTOQUINONE OR EXCHANGED 9,10-ANTHRAQUINONE
J. Biol. Chem., April 1, 2005; 280(13): 12371 - 12381.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2002 by the Biophysical Society.