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Macromolecular Crowding Effects on Reactions of TePixD (Tll0078)

Authors

  • Tsuguyoshi Toyooka,

    1. Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
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  • Keisuke Tanaka,

    1. Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
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  • Koji Okajima,

    1. Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
    2. Research Institute for Advanced Science and Technology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan
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  • Masahiko Ikeuchi,

    1. Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
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  • Satoru Tokutomi,

    1. Research Institute for Advanced Science and Technology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan
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  • Masahide Terazima

    Corresponding author
    1. Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
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  • This paper is part of the Symposium-in-Print on “Blue Light Effects.”

Corresponding author email: mterazima@kuchem.kyoto-u.ac.jp (MasahideTerazima)

Abstract

To reveal macromolecular crowding effects on a chemical reaction of a BLUF (sensors of blue light using FAD) protein (PixD from a thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 [TePixD, Tll0078]), the photoreaction was studied at various concentrations of the macromolecule Ficoll-70 by UV/Vis absorption spectroscopy and the pulsed laser-induced transient grating (TG) method. The absorption spectrum did not change with varying concentration of Ficoll-70. The crowding did not affect the quantum yield of the spectral red shift reaction, recovery rate of the product, rate constant of the volume change reaction and the magnitude of the volume change. However, the magnitude of the TG signal representing the diffusion-sensitive conformation change significantly increased on addition of Ficoll-70. This dependence was attributed to the crowding effect on the TePixD decamer–pentamer equilibrium in the solution. This result indicates that the TePixD reaction is more efficient in cellular than in in vitro conditions.

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