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Time-resolved detection of conformational changes in oat phytochrome A: time-dependent diffusion.

Takeshi Eitoku·Xristo Zarate·Gennady V Kozhukh·Jeong-Il Kim·Pill-Soon Song·Masahide Terazima
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Abstract

Conformational changes in oat phytochrome A (phy) in solution after photoexcitation of the red-absorbing form (Pr) were studied in time-domain by the pulsed laser-induced transient grating technique. It was found that the diffusion coefficient (D) of far-red-absorbing form (Pfr) of large phy (1.3 x 10(-11) m(2) s(-1)) is markedly reduced compared with that of Pr (5.8 x 10(-11) m(2) s(-1)). This large reduction indicates that the conformation of Pfr is significantly changed from that of Pr, so that the intermolecular interaction with water molecules increases. This change completes within 1 ms after the photoexcitation. On the other hand, D of Pr of intact phy (4.1 x 10(-11) m(2) s(-1)) first decreases upon photoexcitation to 0.89 x 10(-11) m(2) s(-1) within 1 ms and then gradually increases with a time constant of 100 ms to the value of Pfr, 1.7 x 10(-11) m(2) s(-1). This slower phase suggests that the conformation of the N-terminal region changes with 100 ms to decrease the intermolecular interaction with water after a global change in the large phy region. The increase of D was interpreted in terms of alpha-helix formation in the Pfr form from the random coil structure in the Pr form.

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AvenaDiffusionDose-Response Relationship, RadiationLightPhytochrome AProtein ConformationRadiation DosageJournal ArticleResearch Support, Non-U.S. Gov't

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Takeshi Eitoku, Xristo Zarate, Gennady V Kozhukh, Jeong-Il Kim, Pill-Soon Song, Masahide Terazima. 2006-08-25. Time-resolved detection of conformational changes in oat phytochrome A: time-dependent diffusion.. https://doi.org/10.1529/biophysj.106.092882

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