Donuts Dissociate

Science Signaling  27 Mar 2012:
Vol. 5, Issue 217, pp. ec99
DOI: 10.1126/scisignal.2003069

In Arabidopsis, the UVR8 protein responds to ultraviolet-B (UV-B) light by dissociating into monomers, which are then available to interact with downstream factors that enact the plant’s response to light. Christie et al. (see the Perspective by Gardner and Correa) have now determined the crystal structure of UVR8. Without ultraviolet-B light, UVR8 dimerizes, with two donut-shaped monomers joined by a network of salt bridges. Close-packing of a pyramid of tryptophan residues permits exciton coupling that is key to UV-B perception. Electron transfer after UV-B perception could dissociate the salt bridges that hold the dimer together and release monomeric UVR8 to initiate light-induced signaling.

J. M. Christie, A. S. Arvai, K. J. Baxter, M. Heilmann, A. J. Pratt, A. O’Hara, S. M. Kelly, M. Hothorn, B. O. Smith, K. Hitomi, G. I. Jenkins, E. D. Getzoff, Plant UVR8 photoreceptor senses UV-B by tryptophan-mediated disruption of cross-dimer salt bridges. Science 335, 1492–1496 (2012). [Abstract] [Full Text]

K. H. Gardner, F. Correa, How plants see the invisible. Science 335, 1451–1452 (2012). [Abstract] [Full Text]