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Kinetic studies on the oxidation of semiquinone and hydroquinone forms of Arabidopsis cryptochrome by molecular oxygen

van Wilderen, LJGW and Silkstone, G and Mason, MG and van Thor, JJ and Wilson, MT (2015) 'Kinetic studies on the oxidation of semiquinone and hydroquinone forms of Arabidopsis cryptochrome by molecular oxygen.' FEBS Open Bio, 5 (1). pp. 885-892. ISSN 2211-5463

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Cryptochromes (crys) are flavoprotein photoreceptors present throughout the biological kingdom that play important roles in plant development and entrainment of the circadian clock in several organisms. Crys non-covalently bind flavin adenine dinucleotide (FAD) which undergoes photoreduction from the oxidised state to a radical form suggested to be active in signalling in vivo. Although the photoreduction reactions have been well characterised by a number of approaches, little is known of the oxidation reactions of crys and their mechanisms. In this work, a stopped-flow kinetics approach is used to investigate the mechanism of cry oxidation in the presence and absence of an external electron donor. This in vitro study extends earlier investigations of the oxidation of Arabidopsis cryptochrome1 by molecular oxygen and demonstrates that, under some conditions, a more complex model for oxidation of the flavin than was previously proposed is required to accommodate the spectral evidence. In the absence of an electron donor, photoreduction leads predominantly to the formation of the radical FADHradical dot. Dark recovery most likely forms flavin hydroperoxide (FADHOOH) requiring superoxide. In the presence of reductant (DTT), illumination yields the fully reduced flavin species (FADH?). Reaction of this with dioxygen leads to transient radical (FADHradical dot) and simultaneous accumulation of oxidised species (FAD), possibly governed by interplay between different cryptochrome molecules or cooperativity effects within the cry homodimer.

Item Type: Article
Uncontrolled Keywords: Stopped-flow; Flavin adenine dinucleotide; Photoreduction; Spectroscopy; Global analysis; Flavin hydroperoxide
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health
Faculty of Science and Health > Life Sciences, School of
SWORD Depositor: Elements
Depositing User: Elements
Date Deposited: 30 Oct 2015 15:02
Last Modified: 06 Jan 2022 13:39

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