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Article Dans Une Revue Proceedings of the National Academy of Sciences of the United States of America Année : 2022

Ultrafast photooxidation of protein-bound anionic flavin radicals

Résumé

The photophysical properties of anionic semireduced flavin radicals are largely unknown despite their importance in numerous biochemical reactions. Here, we studied the photoproducts of these intrinsically unstable species in five different flavoprotein oxidases where they can be stabilized, including the well-characterized glucose oxidase. Using ultrafast absorption and fluorescence spectroscopy, we unexpectedly found that photoexcitation systematically results in the oxidation of protein-bound anionic flavin radicals on a time scale of less than ∼100 fs. The thus generated photoproducts decay back in the remarkably narrow 10- to 20-ps time range. Based on molecular dynamics and quantum mechanics computations, positively charged active-site histidine and arginine residues are proposed to be the electron acceptor candidates. Altogether, we established that, in addition to the commonly known and extensively studied photoreduction of oxidized flavins in flavoproteins, the reverse process (i.e., the photooxidation of anionic flavin radicals) can also occur. We propose that this process may constitute an excited-state deactivation pathway for protein-bound anionic flavin radicals in general. This hitherto undocumented photochemical reaction in flavoproteins further extends the family of flavin photocycles.
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Dates et versions

hal-03582329 , version 1 (04-11-2022)

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Citer

Bo Zhuang, Rivo Ramodiharilafy, Ursula Liebl, Alexey Aleksandrov, Marten H. Vos. Ultrafast photooxidation of protein-bound anionic flavin radicals. Proceedings of the National Academy of Sciences of the United States of America, 2022, 119 (8), pp.e2118924119. ⟨10.1073/pnas.2118924119⟩. ⟨hal-03582329⟩
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