Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Plant Cell. 2012 Sep;24(9):3755-66. doi: 10.1105/tpc.112.101451. Epub 2012 Sep 25.
Arabidopsis thaliana UV RESISTANCE LOCUS8 (UVR8) is a photoreceptor specifically for UV-B light that initiates photomorphogenic responses in plants. UV-B exposure causes rapid conversion of UVR8 from dimer to monomer, accumulation in the nucleus, and interaction with CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), which functions with UVR8 in UV-B responses. Studies in yeast and with purified UVR8 implicate several tryptophan amino acids in UV-B photoreception. However, their roles in UV-B responses in plants, and the functional significance of all 14 UVR8 tryptophans, are not known. Here we report the functions of the UVR8 tryptophans in vivo. Three tryptophans in the β-propeller core are important in maintaining structural stability and function of UVR8. However, mutation of three other core tryptophans and four at the dimeric interface has no apparent effect on function in vivo. Mutation of three tryptophans implicated in UV-B photoreception, W233, W285, and W337, impairs photomorphogenic responses to different extents. W285 is essential for UVR8 function in plants, whereas W233 is important but not essential for function, and W337 has a lesser role. Ala mutants of these tryptophans appear monomeric and constitutively bind COP1 in plants, but their responses indicate that monomer formation and COP1 binding are not sufficient for UVR8 function.
拟南芥紫外线抵抗 8 号（UVR8）是一种专门用于 UV-B 光的光受体，它在植物中启动光形态建成反应。UV-B 暴露会导致 UVR8 迅速从二聚体转化为单体，在核内积累，并与 CONSTITUTIVELY PHOTOMORPHOGENIC1（COP1）相互作用，COP1 在 UV-B 反应中与 UVR8 一起发挥作用。酵母研究和纯化的 UVR8 表明，几个色氨酸氨基酸参与 UV-B 光受体。然而，它们在植物中 UV-B 反应中的作用，以及 UVR8 中所有 14 个色氨酸的功能意义尚不清楚。在这里，我们报告了 UVR8 色氨酸在体内的功能。β-螺旋桨核心中的三个色氨酸对维持 UVR8 的结构稳定性和功能很重要。然而，三个其他核心色氨酸和两个二聚体界面的色氨酸突变对体内功能没有明显影响。参与 UV-B 光受体的三个色氨酸突变，W233、W285 和 W337，在不同程度上损害了光形态建成反应。W285 对 UVR8 在植物中的功能是必需的，而 W233 虽然重要但不是必需的，W337 的作用较小。这些色氨酸的 Ala 突变体在植物中似乎是单体的并且持续地与 COP1 结合，但它们的反应表明单体形成和 COP1 结合对于 UVR8 功能是不够的。
