title: Structural basis of ultraviolet-B perception by UVR8.
abstract: The Arabidopsis thaliana protein UVR8 is a photoreceptor for ultraviolet-B. Upon ultraviolet-B irradiation, UVR8 undergoes an immediate switch from homodimer to monomer, which triggers a signalling pathway for ultraviolet protection. The mechanism by which UVR8 senses ultraviolet-B remains largely unknown. Here we report the crystal structure of UVR8 at 1.8 Å resolution, revealing a symmetric homodimer of seven-bladed β-propeller that is devoid of any external cofactor as the chromophore. Arginine residues that stabilize the homodimeric interface, principally Arg 286 and Arg 338, make elaborate intramolecular cation-π interactions with surrounding tryptophan amino acids. Two of these tryptophans, Trp 285 and Trp 233, collectively serve as the ultraviolet-B chromophore. Our structural and biochemical analyses identify the molecular mechanism for UVR8-mediated ultraviolet-B perception, in which ultraviolet-B radiation results in destabilization of the intramolecular cation-π interactions, causing disruption of the critical intermolecular hydrogen bonds mediated by Arg 286 and Arg 338 and subsequent dissociation of the UVR8 homodimer.
authors.affiliation: Tsinghua-Peking Center for Life Sciences, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China.
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.forename: Qi
authors.initials: Q
authors.lastname: Hu
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yan
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.forename: Chuangye
authors.initials: C
authors.lastname: Yan
authors.forename: Xi
authors.initials: X
authors.lastname: Huang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Panyu
authors.initials: P
authors.lastname: Yang
authors.forename: Haiteng
authors.initials: H
authors.lastname: Deng
authors.forename: Jiawei
authors.initials: J
authors.lastname: Wang
authors.forename: XingWang
authors.initials: X
authors.lastname: Deng
authors.forename: Yigong
authors.initials: Y
authors.lastname: Shi
mesh_terms: D017360:Arabidopsis / Q000737:chemistry*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000528:radiation effects*; D002412:Cations / Q000737:chemistry; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000528:radiation effects*; D018360:Crystallography, X-Ray; D055537:Light Signal Transduction / Q000528:radiation effects*; D008958:Models, Molecular; D011487:Protein Conformation / Q000528:radiation effects; D055503:Protein Multimerization / Q000528:radiation effects; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; D002412:Cations; D002868:Chromosomal Proteins, Non-Histone; C525052:Uvr8 protein, Arabidopsis; D014364:Tryptophan