Jump to main content
Jump to site search

Issue 5, 2015
Previous Article Next Article

Reaction dynamics of the UV-B photosensor UVR8

Author affiliations

Abstract

UVR8 is a recently discovered ultraviolet-B (UV-B) photoreceptor protein identified in plants and algae. In the dark state, UVR8 exists as a homodimer, whereas UV-B irradiation induces UVR8 monomerization and initiation of signaling. Although the biological functions of UVR8 have been studied, the fundamental reaction mechanism and associated kinetics have not yet been fully elucidated. Here, we used the transient grating method to determine the reaction dynamics of UVR8 monomerization based on its diffusion coefficient. We found that the UVR8 photodissociation reaction proceeds in three stages: (i) photoexcitation of cross-dimer tryptophan (Trp) pyramids; (ii) an initial conformational change with a time constant of 50 ms; and (iii) dimer dissociation with a time constant of 200 ms. We identified W285 as the key Trp residue responsible for initiating this photoreaction. Although the C-terminus of UVR8 is essential for biological interactions and signaling via downstream components such as COP1, no obvious differences were detected between the photoreactions of wild-type UVR8 (amino acids 1–440) and a mutant lacking the C-terminus (amino acids 1–383). This similarity indicates that the conformational change associated with stage ii cannot primarily be attributed to this region. A UV-B-driven conformational change with a time constant of 50 ms was also detected in the monomeric mutants of UVR8. Dimer recovery following monomerization, as measured by circular dichroism spectroscopy, was decreased under oxygen-purged conditions, suggesting that redox reactivity is a key factor contributing to the UVR8 oligomeric state.

Graphical abstract: Reaction dynamics of the UV-B photosensor UVR8

Back to tab navigation

Supplementary files

Publication details

The article was received on 09 Jan 2015, accepted on 10 Mar 2015 and first published on 10 Mar 2015


Article type: Paper
DOI: 10.1039/C5PP00012B
Author version available: Download Author version (PDF)
Citation: Photochem. Photobiol. Sci., 2015,14, 995-1004
  •   Request permissions

    Reaction dynamics of the UV-B photosensor UVR8

    T. Miyamori, Y. Nakasone, K. Hitomi, J. M. Christie, E. D. Getzoff and M. Terazima, Photochem. Photobiol. Sci., 2015, 14, 995
    DOI: 10.1039/C5PP00012B

Search articles by author

Spotlight

Advertisements