西亚试剂：Structural basis of ultraviolet-B perception by UVR8

Structural basis of ultraviolet-B perception by UVR8

Di Wu, Qi Hu, Zhen Yan, Wen Chen, Chuangye Yan, Xi Huang, Jing Zhang, Panyu Yang, Haiteng Deng, Jiawei Wang, XingWang Deng & Yigong Shi

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 A 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 Arg286 and Arg338, make elaborate intramolecular cation–π interactions with surrounding tryptophan amino acids. Two of these tryptophans, Trp285 and Trp233, 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 Arg286 and Arg338 and subsequent dissociation of the UVR8 homodimer.