{
  "id": 4881037,
  "title": "Mapping Light-Induced Conformational Dynamics of Pigeon Cryptochrome 4 by HDX-MS: Structural Transitions from Spin Pair Formation to Activated Conformational States",
  "url": "https://urgent.news/2026/09/01/mapping-light-induced-conformational-dynamics-of-pigeon-cryptochrome",
  "topic": "science",
  "section": "Science",
  "published": "2026-09-01T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.08.27.747556v1?rss=1"
  },
  "original_language": "en",
  "account": "Researchers have investigated the structural dynamics of pigeon cryptochrome 4 (ClCRY4) in response to light, aiming to understand the connection between light-dependent radical-pair chemistry and its signaling role. Utilizing steady-state UV-visible spectroscopy and hydrogen-deuterium exchange mass spectrometry (HDX-MS), the team discovered that lower temperatures slow FAD photoreduction, extending the duration of the FAD neutral semiquinone signaling state. This finding suggests that conformational changes, rather than proton transfer, are the primary factors governing the rate of FAD neutral semiquinone formation.\n\nBy employing a pump-probe HDX-MS approach at 10°C, the researchers identified eight peptides within ClCRY4 that exhibit rapid and sustained light-induced protection. These peptides are located within the phosphate-binding loop, protrusion motif, electron-transfer-chain loops, and C-terminal tail, marking the sites of early conformational rearrangements that precede FAD neutral semiquinone accumulation.\n\nAdditionally, the study reveals a bimodal pattern of deuterium uptake in the phosphate-binding loop, indicating a local redistribution of conformational substates on the time scale of signaling species accumulation. Site-specific mutagenesis within the C-terminal tail supports these findings, leading to a model in which blue light triggers rapid clamping of the protein near two regions of spin pair separation. Subsequently, a rate-limiting closure of a surface loop occurs.\n\nThe resolution of time-dependent structural transitions that follow photoactivation of ClCRY4 sheds light on the interface between quantum radical-pair formation and classical conformational changes. This work unveils a more comprehensive structural framework for the molecular events underlying avian magnetoreception.",
  "summary": "The navigational prowess of migratory birds is thought to arise from light-dependent radical-pair chemistry in cryptochrome 4 (CRY4), yet the slow structural transitions that couple photochemistry to signaling remain elusive. Here, we combine temperature-controlled steady-state UV-visible spectroscopy and hydrogen-deuterium exchange mass spectrometry (HDX-MS) to elucidate the photochemical and…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}