Rapid Oxidation Following Photoreduction in the Avian Cryptochrome4 Photocycle
| Autor: | Hiromasa Mitsui, Kota Miura, Yasushi Imamoto, Hiroaki Otsuka, Keiko Okano, Toshiyuki Okano |
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| Rok vydání: | 2020 |
| Předmět: |
Free Radicals
Light Radical Protonation Flavin group Photochemistry Biochemistry Dithiothreitol Avian Proteins 03 medical and health sciences chemistry.chemical_compound Molecule Animals 0303 health sciences Photolysis Chemistry 030302 biochemistry & molecular biology Photodissociation Magnetoreception Cryptochromes Flavin-Adenine Dinucleotide Flash photolysis Tyrosine Chickens Oxidation-Reduction |
| Zdroj: | Biochemistry. 59(38) |
| ISSN: | 1520-4995 |
| Popis: | Avian magnetoreception is assumed to occur in the retina. Although its molecular mechanism is unclear, magnetic field-dependent formation and the stability of radical-containing photointermediate(s) are suggested to play key roles in a hypothesis called the radical pair mechanism. Chicken cryptochrome4 (cCRY4) has been identified as a candidate magnetoreceptive molecule due to its expression in the retina and its ability to form stable flavin neutral radicals (FADH●) upon blue light absorption. Herein, we used millisecond flash photolysis to investigate the cCRY4 photocycle, in both the presence and absence of dithiothreitol (DTT); detecting the anion radical form of FAD (FAD●-) under both conditions. Using spectral data obtained during flash photolysis and UV-visible photospectroscopy, we estimated the absolute absorbance spectra of the photointermediates, thus allowing us to decompose each spectrum into its individual components. Notably, in the absence of DTT, approximately 37% and 63% of FAD●- was oxidized to FADOX and protonated to form FADH●, respectively. Singular value decomposition analysis suggested the presence of two FAD●- molecular species, each of which was destined to be oxidized to FADOX or protonated to FADH●. A tyrosine neutral radical was also detected; however, it likely decayed concomitantly with the oxidation of FAD●-. On the basis of these results, we considered the occurrence of bifurcation prior to FAD●- generation, or during FAD●- oxidization, and discussed the potential role played by the tyrosine radical in the radical pair mechanism. |
| Databáze: | OpenAIRE |
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