Abstract
The recently identified plant photoreceptor UVR8 (UV RESISTANCE LOCUS 8) triggers regulatory changes in gene expression in response to ultraviolet-B (UV-B) light through an unknown mechanism. Here, crystallographic and solution structures of the UVR8 homodimer, together with mutagenesis and far-UV circular dichroism spectroscopy, reveal its mechanisms for UV-B perception and signal transduction. β-propeller subunits form a remarkable, tryptophan-dominated, dimer interface stitched together by a complex salt-bridge network. Salt-bridging arginines flank the excitonically coupled cross-dimer tryptophan "pyramid" responsible for UV-B sensing. Photoreception reversibly disrupts salt bridges, triggering dimer dissociation and signal initiation. Mutation of a single tryptophan to phenylalanine retunes the photoreceptor to detect UV-C wavelengths. Our analyses establish how UVR8 functions as a photoreceptor without a prosthetic chromophore to promote plant development and survival in sunlight.
Publication types
-
Research Support, N.I.H., Extramural
-
Research Support, Non-U.S. Gov't
-
Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
-
Arabidopsis / physiology
-
Arabidopsis Proteins / chemistry*
-
Arabidopsis Proteins / genetics
-
Arabidopsis Proteins / metabolism*
-
Arginine / chemistry
-
Chromosomal Proteins, Non-Histone / chemistry*
-
Chromosomal Proteins, Non-Histone / genetics
-
Chromosomal Proteins, Non-Histone / metabolism*
-
Circular Dichroism
-
Crystallography, X-Ray
-
Hydrogen Bonding
-
Hydrogen-Ion Concentration
-
Light Signal Transduction
-
Models, Molecular
-
Mutagenesis
-
Photoreceptors, Plant / chemistry*
-
Photoreceptors, Plant / genetics
-
Photoreceptors, Plant / metabolism*
-
Protein Conformation
-
Protein Multimerization
-
Recombinant Fusion Proteins / chemistry
-
Recombinant Fusion Proteins / metabolism
-
Tryptophan / chemistry
-
Ultraviolet Rays*
Substances
-
Arabidopsis Proteins
-
Chromosomal Proteins, Non-Histone
-
Photoreceptors, Plant
-
Recombinant Fusion Proteins
-
Uvr8 protein, Arabidopsis
-
Tryptophan
-
Arginine