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Conformational switching in the fungal light sensor Vivid.
Brian D Zoltowski1, Carsten Schwerdtfeger, Joanne Widom
1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
Science (New York, N.Y.)
|May 19, 2007
Summary
The Neurospora crassa Vivid protein
Area of Science:
- Molecular biology
- Biochemistry
- Structural biology
Background:
- The Neurospora crassa photoreceptor Vivid plays a crucial role in regulating blue-light responses and the circadian clock.
- Understanding the structural and mechanistic basis of Vivid's light sensing is essential for deciphering its biological functions.
Purpose of the Study:
- To elucidate the structural mechanisms underlying the light-induced activation of the Neurospora crassa Vivid photoreceptor.
- To investigate the role of specific amino acid residues and cofactor interactions in Vivid's signaling pathway.
Main Methods:
- X-ray crystallography was employed to determine the high-resolution structures of Vivid in both dark and light states.
- Biochemical assays were performed to analyze the photoinduced formation of a cystein-flavin adduct and its impact on protein conformation.
- Site-directed mutagenesis was used to probe the function of key residues, including a cysteine-to-serine substitution.
Main Results:
- Crystal structures revealed a unique Per-Arnt-Sim domain with an N-terminal cap and a loop accommodating the flavin cofactor.
- Photoinduced formation of a cystein-flavin adduct leads to flavin protonation and an N-terminal conformational change, activating Vivid.
- A cysteine-to-serine mutation abolished light-induced signaling, demonstrating the critical role of this residue in the activation mechanism.
Conclusions:
- The study reveals a novel light-activation mechanism for Vivid involving cystein-flavin adduct formation and conformational changes.
- Key structural and mechanistic elements of Vivid activation are conserved in other related photosensors, suggesting a common evolutionary origin.
- These findings provide critical insights into the function of Vivid and related blue-light photoreceptors in regulating biological processes.
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