Time‐Resolved Native Mass Spectrometry Reveals Reversible Light‐Driven Oligomerization of Arabidopsis Cryptochrome 1 and Its Antagonism by BIC1

Apr 7, 2026Angewandte Chemie (International ed. in English)

Light Causes Reversible Clumping of a Plant Light Sensor Protein, Opposed by BIC1

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Abstract

Blue light triggers the reversible assembly of cryptochrome 1 (CRY1) into tetramers, with ATP enhancing this process.

CRY1-PHR forms dimers that further assemble into tetramers through a reversible pathway.
A quantitative two-step kinetic model describes the relationship between light-induced oligomerization and thermal disassembly.
ATP accelerates the formation of tetramers and stabilizes oligomers by influencing the photochemistry of the flavin adenine dinucleotide (FAD) chromophore.
The Blue-light Inhibitor of Cryptochromes 1 (BIC1) binds to CRY1-PHR with higher affinity in blue light, preventing oligomerization.
BIC1 actively disassembles pre-formed tetramers in a light-independent manner, regardless of the redox state of CRY.

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Cryptochromes (CRYs) are blue-light photoreceptors that mediate light-dependent signaling in plants. Here, we uncover the molecular mechanism underlying blue-light activation of the Arabidopsis thaliana cryptochrome 1 photolyase homology region (CRY1-PHR) using time-resolved native mass spectrometry combined with kinetic modeling. This approach enables direct monitoring of light-driven complex formation with temporal and molecular resolution. We show that blue-light activation of CRY1-PHR follows a reversible assembly pathway in which monomers rapidly form dimers that further assemble into tetramers. A quantitative two-step kinetic model captures the dynamic interplay between light-induced oligomerization and thermal disassembly. Strikingly, ATP accelerates tetramer formation and stabilizes oligomers by tuning the underlying photochemistry of the flavin adenine dinucleotide (FAD) chromophore. In contrast, the Blue-light Inhibitor of Cryptochromes 1 (BIC1) acts as a potent antagonist. BIC1 binds to CRY1-PHR even in the dark, with significantly increased affinity under blue light, thereby inhibiting oligomerization and actively disassembling pre-formed tetramers. This disassembly is light-independent and occurs regardless of CRY's redox state. Together, these findings provide a kinetic and mechanistic framework for reversible blue-light signaling by plant CRYs and highlight how opposing regulators precisely modulate photoreceptor activation at the molecular level.

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Time‐Resolved Native Mass Spectrometry Reveals Reversible Light‐Driven Oligomerization of Arabidopsis Cryptochrome 1 and Its Antagonism by BIC1

Abstract

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