Directing electron transfer within Photosystem I by breaking H-bonds in the cofactor branches

Yajing Li, Art Van Der Est, Marie Gabrielle Lucas, V. M. Ramesh, Feifei Gu, Alexander Petrenko, Su Lin, Andrew Webber, Fabrice Rappaport, Kevin Redding

    Research output: Contribution to journalArticle

    59 Citations (Scopus)

    Abstract

    Photosystem I has two branches of cofactors down which light-driven electron transfer (ET) could potentially proceed, each consisting of a pair of chlorophylls (Chls) and a phylloquinone (PhQ). Forward ET from PhQ to the next ET cofactor (Fx) is described by two kinetic components with decay times of ≈20 and ≈200 ns, which have been proposed to represent ET from PhQB and PhQA, respectively. Immediately preceding each quinone is a Chl (ec3), which receives a H-bond from a nearby tyrosine. To decrease the reduction potential of each of these Chls, and thus modify the relative yield of ET within the targeted branch, this H-bond was removed by conversion of each Tyr to Phe in the green alga Chlamydomonas reinhardtii. Together, transient optical absorption spectroscopy performed in vivo and transient electron paramagnetic resonance data from thylakoid membranes showed that the mutations affect the relative amplitudes, but not the lifetimes, of the two kinetic components representing ET from PhQ to Fx. The mutation near ec3A increases the fraction of the faster component at the expense of the slower component, with the opposite effect seen in the ec3B mutant. We interpret this result as a decrease in the relative use of the targeted branch. This finding suggests that in Photosystem I, unlike type II reaction centers, the relative efficiency of the two branches is extremely sensitive to the energetics of the embedded redox cofactors.

    Original languageEnglish (US)
    Pages (from-to)2144-2149
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume103
    Issue number7
    DOIs
    StatePublished - Feb 14 2006

    Fingerprint

    Photosystem I Protein Complex
    Electrons
    Vitamin K 1
    Chlamydomonas reinhardtii
    Mutation
    Chlorophyta
    Thylakoids
    Electron Spin Resonance Spectroscopy
    Chlorophyll
    Oxidation-Reduction
    Tyrosine
    Spectrum Analysis
    Light

    Keywords

    • Chlamydomonas
    • Directionality
    • Photosynthetic reaction center
    • Pump-probe spectroscopy
    • Transient EPR

    ASJC Scopus subject areas

    • Genetics
    • General

    Cite this

    Directing electron transfer within Photosystem I by breaking H-bonds in the cofactor branches. / Li, Yajing; Van Der Est, Art; Lucas, Marie Gabrielle; Ramesh, V. M.; Gu, Feifei; Petrenko, Alexander; Lin, Su; Webber, Andrew; Rappaport, Fabrice; Redding, Kevin.

    In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 103, No. 7, 14.02.2006, p. 2144-2149.

    Research output: Contribution to journalArticle

    Li, Yajing ; Van Der Est, Art ; Lucas, Marie Gabrielle ; Ramesh, V. M. ; Gu, Feifei ; Petrenko, Alexander ; Lin, Su ; Webber, Andrew ; Rappaport, Fabrice ; Redding, Kevin. / Directing electron transfer within Photosystem I by breaking H-bonds in the cofactor branches. In: Proceedings of the National Academy of Sciences of the United States of America. 2006 ; Vol. 103, No. 7. pp. 2144-2149.
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