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UV-B resistance 8 (UVR8) also known as ultraviolet-B receptor UVR8 is an UV-B – sensing protein found in plants and possibly other sources.[2] It is responsible for sensing ultraviolet light in the range 280-315 nm and initiating the plant stress response. UVR8 was first identified as a crucial mediator of a plant's response to UV-B in Arabidopsis thaliana containing a mutation in this protein. This plant was found to have a hypersensitivity to UV-B[3] which damages DNA. UVR8 is thought to be a unique photoreceptor as it doesn't contain a prosthetic chromophore but its light-sensing ability is intrinsic to the molecule.[4] Tryptophan (Trp) residue 285 has been suggested to act the UV-B sensor, while other Trp residues have been also seen to be involved (Trp233 > Trp337 > Trp94) although in-vivo data suggests that Trp285 and Trp233 are most important.[2]

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