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| Format: | Preprint |
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2026
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| Online-Zugang: | https://arxiv.org/abs/2604.19579 |
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| _version_ | 1866917432470274048 |
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| author | Kish, Monika Pradhan, Suchitra Ramsay, Jessica L. Salazar, Paloma Munguía Phillips, Jonathan Kattnig, Daniel R. |
| author_facet | Kish, Monika Pradhan, Suchitra Ramsay, Jessica L. Salazar, Paloma Munguía Phillips, Jonathan Kattnig, Daniel R. |
| contents | The light-dependent magnetic compass of night-migratory songbirds is widely hypothesized to rely on the radical pair mechanism within retinal cryptochrome. However, bridging the mechanistic gap between microsecond quantum spin dynamics and the long-lived, global protein conformational changes required for cellular signalling remains a formidable challenge. Here, we apply redox state-resolved hydrogen/deuterium-exchange mass spectrometry (HDX-MS) to map the conformational landscape of European robin cryptochrome 4a (ErCry4a) across its photocycle. We reveal that photochemical reduction drives robust, allosteric structural transitions across key functional nodes, including the phosphate-binding loop (PBL), protrusion loop (PL), FAD-proximal helix α17, and the C-terminal α22/α23 network. Crucially, we isolate the structural fingerprint of the transient semiquinone, the presumed signalling species. Rather than acting as a linear structural stepping-stone, the semiquinone exhibits a distinct, non-monotonic conformational signature characterized by a transient destabilization of the PBL and PL, contrasting sharply with the global rigidification observed in the fully reduced state. These findings establish the semiquinone as a structurally unique and functionally competent biological entity. Our results provide direct biophysical evidence for a dedicated, high-fidelity structural signalling cascade, detailing how localized quantum-level photochemistry is translated into the precise conformational dynamics required for animal navigation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_19579 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Distinct Structural Dynamics of the Semiquinone State Define a Signalling Pathway in Avian Cryptochrome Kish, Monika Pradhan, Suchitra Ramsay, Jessica L. Salazar, Paloma Munguía Phillips, Jonathan Kattnig, Daniel R. Biological Physics Chemical Physics The light-dependent magnetic compass of night-migratory songbirds is widely hypothesized to rely on the radical pair mechanism within retinal cryptochrome. However, bridging the mechanistic gap between microsecond quantum spin dynamics and the long-lived, global protein conformational changes required for cellular signalling remains a formidable challenge. Here, we apply redox state-resolved hydrogen/deuterium-exchange mass spectrometry (HDX-MS) to map the conformational landscape of European robin cryptochrome 4a (ErCry4a) across its photocycle. We reveal that photochemical reduction drives robust, allosteric structural transitions across key functional nodes, including the phosphate-binding loop (PBL), protrusion loop (PL), FAD-proximal helix α17, and the C-terminal α22/α23 network. Crucially, we isolate the structural fingerprint of the transient semiquinone, the presumed signalling species. Rather than acting as a linear structural stepping-stone, the semiquinone exhibits a distinct, non-monotonic conformational signature characterized by a transient destabilization of the PBL and PL, contrasting sharply with the global rigidification observed in the fully reduced state. These findings establish the semiquinone as a structurally unique and functionally competent biological entity. Our results provide direct biophysical evidence for a dedicated, high-fidelity structural signalling cascade, detailing how localized quantum-level photochemistry is translated into the precise conformational dynamics required for animal navigation. |
| title | Distinct Structural Dynamics of the Semiquinone State Define a Signalling Pathway in Avian Cryptochrome |
| topic | Biological Physics Chemical Physics |
| url | https://arxiv.org/abs/2604.19579 |