The ionic and protonation states of flavin control the activation and recovery of Drosophila cryptochrome

The ionic and protonation states of flavin control the activation and recovery of Drosophila cryptochrome | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article The ionic and protonation states of flavin control the activation and recovery of Drosophila cryptochrome Lei Xu, Wenlong Xie, Mengqi Wan, Yuting Dai, Yingjun Jiang, Mohan Wang, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6433704/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Drosophila cryptochrome (dCry) is a flavin-containing photoreceptor that entrains the circadian clock with light. The C-terminal tail (CTT) release upon illumination is a crucial step for light signal transduction of dCry. Here, we demonstrated that both anionic semiquinone (asq) and anionic hydroquinone (hq) formed during illumination (the latter only obtained in dCry mutants) could trigger CTT release. Meanwhile, neutral semiquinone (nsq) formation suppressed CTT release. However, it was observed that a fraction of nsq was formed during photoreduction of dCry at neutral conditions. Nevertheless, the nsq fraction of dCry was increased during photoreduction under acidic pH conditions, accompanied with inhibition of CTT release. Evidence suggested that the proton required for nsq formation was transferred to flavin through a side tunnel, which is a structural feature that does not exist in the homologs of dCry, eukaryotic 6 − 4 photolyases. The nsq formation was minimized in dCry under basic conditions, or the mutants in CTT, which resulted enhanced CTT release, but slower oxidation after photoreduction. Therefore, forming a proper fraction of nsq is important for fast recovery of dCry after light sensing. Nevertheless, a key residue at the side tunnel, His378, was found to be a proton interceptor that adjusted the nsq formation. Biological sciences/Biochemistry/Proteins/Circadian rhythm signalling peptides and proteins Biological sciences/Chemical biology/Biophysical chemistry flavin light sensing photochemistry proton transferring cryptochrome Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SI2g.docx Supporting Information Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6433704","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":442746420,"identity":"2c4b7914-19e1-4f74-87db-c281bf40b078","order_by":0,"name":"Lei 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