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Photoactivation femtoseconde de deux nouvelles protéines de la famille des cryptochrome/photolyase, issues de l’algue verte Ostreococcus tauri. Photocycle ultrarapide et état signalant de la photophobie du protozoaire Blepharisma japonicum

Abstract : i) This work deals with the photoactivity of two new flavoproteins (OtCPF1 and OtCPF2) of the green alga Ostreococcus tauri, belonging to the Cryptochrome Photolyase Family (CPF). In both cases, we observed an ultrafast electron transfer (OtCPF1: 390fs ; OtCPF2: 590fs) after excitation of the chromophore flavin adenine dinucleotide (FAD) in its oxidized form. We characterized a tryptophan residue as the electron donor. We explain the subsequent kinetics by electron transfer steps along a chain of three tryptophan residues, a well conserved structure among the CPF proteins. We also analyzed the energy transfer from the photoantenna of OtCPF2 to FAD in its oxidized and reduced form. The structural analysis, done by homology modeling, allowed us to rationalize the spectroscopic results. ii) To explain the very short-lived photocycle observed for OBIP, the putative photoreceptor of the protozoan Blepharisma japonicum, we proposed an original model involving an ultrafast equilibrium between the locally excited state of the chromophore (Oxyblepharismin) hydrogen bonded to a closellying residue and an intermolecular charge transfer state. We have also proposed that the signaling state of the photophobic response could be the deprotonated Oxyblepharismin chromophore.
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https://tel.archives-ouvertes.fr/tel-03184590
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Submitted on : Monday, March 29, 2021 - 4:12:42 PM
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Johanna Brazard. Photoactivation femtoseconde de deux nouvelles protéines de la famille des cryptochrome/photolyase, issues de l’algue verte Ostreococcus tauri. Photocycle ultrarapide et état signalant de la photophobie du protozoaire Blepharisma japonicum. Autre. Université Pierre et Marie Curie (Paris, France), 2009. Français. ⟨NNT : 2009PA066368⟩. ⟨tel-03184590⟩

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