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GKSWVSPAERYAVVPDETGLTDGSSKG (UVR8 C-terminal 27-residue fragment). The peptide corresponds to amino acids 397–423 of the UV-B photoreceptor protein UVR8 in Arabidopsis thaliana, commonly denoted as UVR8^C27. UVR8 operates as a UV-B-specific photoreceptor that exists as an inactive homodimer under normal conditions. Upon absorption of UV-B light, UVR8 monomerizes and interacts with the E3 ubiquitin ligase COP1, initiating UV-B signaling and photomorphogenic development. The UVR8 C-terminal 27-residue segment alone is sufficient to sustain the interaction with COP1 and regulate UV-B-dependent responses.
Functional & Experimental Applications
- Despite being intrinsically disordered, UVR8^C27 adopts more structured conformations at elevated temperatures, as observed via CD spectroscopy and NMR studies.
- Computational simulations revealed an inverted free energy landscape: the peptide’s lowest-energy state is disordered, yet structured conformations are accessible at higher energies.
- A key proline residue at position 411 (P411) plays a critical role in stabilizing this disordered, low-energy state and acts as a structural barrier that prevents α-helix propagation from the C-terminus inward.
- UVR8^C27 functions as a molecular switch, with its conformational flexibility enabling interaction with COP1 and facilitating UV-B signal transduction.
This peptide exemplifies how structural disorder and intrinsic flexibility serve as adaptative features for protein–protein interactions in cellular signaling pathways, specifically enabling UVR8 to act as a dynamic photoreceptor module.
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