Exploring the electron transfer pathways in photosystem I by high-time-resolution electron paramagnetic resonance: observation of the B-side radical pair P700(+)A1B(-) in whole cells of the deuterated green alga Chlamydomonas reinhardtii at cryogenic temperatures. (Articolo in rivista)

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  • Exploring the electron transfer pathways in photosystem I by high-time-resolution electron paramagnetic resonance: observation of the B-side radical pair P700(+)A1B(-) in whole cells of the deuterated green alga Chlamydomonas reinhardtii at cryogenic temperatures. (Articolo in rivista) (literal)
Anno
  • 2012-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1021/ja208806g (literal)
Alternative label
  • Berthold T, von Gromoff ED, Santabarbara S, Stehle P, Link G, Poluektov OG, Heathcote P, Beck CF, Thurnauer MC, Kothe G. (2012)
    Exploring the electron transfer pathways in photosystem I by high-time-resolution electron paramagnetic resonance: observation of the B-side radical pair P700(+)A1B(-) in whole cells of the deuterated green alga Chlamydomonas reinhardtii at cryogenic temperatures.
    in Journal of the American Chemical Society (Print)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Berthold T, von Gromoff ED, Santabarbara S, Stehle P, Link G, Poluektov OG, Heathcote P, Beck CF, Thurnauer MC, Kothe G. (literal)
Pagina inizio
  • 5563 (literal)
Pagina fine
  • 5576 (literal)
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  • http://pubs.acs.org/doi/abs/10.1021/ja208806g (literal)
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  • 134 (literal)
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  • 13 (literal)
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  • 12 (literal)
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  • ISI Web of Science (WOS) (literal)
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  • Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg, Germany Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States (literal)
Titolo
  • Exploring the electron transfer pathways in photosystem I by high-time-resolution electron paramagnetic resonance: observation of the B-side radical pair P700(+)A1B(-) in whole cells of the deuterated green alga Chlamydomonas reinhardtii at cryogenic temperatures. (literal)
Abstract
  • Crystallographic models of photosystem I (PS I) highlight a symmetrical arrangement of the electron transfer cofactors which are organized in two parallel branches (A, B) relative to a pseudo-C-2 symmetry axis that is perpendicular to the membrane plane. Here, we explore the electron transfer pathways of PS I in whole cells of the deuterated green alga Chlamydomonas reinhardtii using high-time-resolution electron paramagnetic resonance (EPR) at cryogenic temperatures. Particular emphasis is given to quantum oscillations detectable in the tertiary radical pairs P(700)(+)A(1A)(-) and P(700)(+)A(1B)(-) of the electron transfer chain. Results are presented first for the deuterated site-directed mutant PsaA-M684H in which electron transfer beyond the primary electron acceptor A(0A) on the PsaA branch of electron transfer is impaired. Analysis of the quantum oscillations, observed in a two-dimensional Q-band (34 GHz) EPR experiment, provides the geometry of the B-side radical pair. The orientation of the g tensor of P-700(+) in an external reference system is adapted from a time-resolved multifrequency EPR study of deuterated and N-15-substituted cyanobacteria (Link, G.; Berthold, T.; Bechtold, M.; Weidner, J.-U.; Ohmes, E.; Tang, J.; Poluektov, O.; Utschig, L.; Schlesselman, S. L.; Thurnauer, M. C.; Kothe, G. J. Am. Chem, Soc. 2001, 123, 4211-4222). Thus, we obtain the three-dimensional structure of the B-side radical pair following photoexcitation of PS I in its native membrane. The new structure describes the position and orientation of the reduced B-side quinone A(1B)(-) on a nanosecond time scale after light-induced charge separation. Furthermore, we present results for deuterated wild-type cells of C. reinhardtii demonstrating that both radical Pairs P(700)(+)A(1A)(-) and P(700)(+)A(1B)(-) participate in the electron transfer process according to a mole ratio of 0.71/0.29 in favor of P(700)(+)A(1A)(-). A detailed comparison reveals different orientations of A(1A)(-) and A(1B)(-) in their respective binding sites such that formation of a strong hydrogen bond from A(1)(-) to the protein backbone is possible only in the case of A(1A)(-). We suggest that this is relevant to the rates of forward electron transfer from A(1A)(-) or A(1B)(-) to the iron-sulfur center F-x, which differ by a factor of 10. Thus, the present study sheds new light on the orientation of the phylloquinone acceptors in their binding pockets in PS I and the effect this has on function. (literal)
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