Feng Juan, Zhao Shun, Chen Xuemin, Wang Wenda, Dong Wei, Chen Jinghua, Shen Jian-Ren, Liu Lin, Kuang Tingyun
Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Haidian District, Beijing 100093, People's Republic of China.
Acta Crystallogr D Biol Crystallogr. 2015 Feb;71(Pt 2):367-75. doi: 10.1107/S1399004714026091. Epub 2015 Jan 23.
Hexokinase 1 from Arabidopsis thaliana (AtHXK1) plays a dual role in glycolysis and sugar sensing for vital metabolic and physiological processes. The uncoupling of glucose signalling from glucose metabolism was demonstrated by the analysis of two mutants (AtHXK1(G104D) and AtHXK1(S177A)) that are catalytically inactive but still functional in signalling. In this study, substrate-binding experiments indicate that the two catalytically inactive mutants have a high affinity for glucose, and an ordered substrate-binding mechanism has been observed for wild-type AtHXK1. The structure of AtHXK1 was determined both in its inactive unliganded form and in its active glucose-bound form at resolutions of 1.8 and 2.0 Å, respectively. These structures reveal a domain rearrangement of AtHXK1 upon glucose binding. The 2.1 Å resolution structure of AtHXK1(S177A) in the glucose-bound form shows similar glucose-binding interactions as the wild type. A glucose-sensing network has been proposed based on these structures. Taken together, the results provide a structural explanation for the dual functions of AtHXK1.
拟南芥己糖激酶1（AtHXK1）在糖酵解和糖感知过程中发挥双重作用，对重要的代谢和生理过程至关重要。通过对两个催化无活性但仍具有信号传导功能的突变体（AtHXK1(G104D)和AtHXK1(S177A)）的分析，证明了葡萄糖信号传导与葡萄糖代谢的解偶联。在本研究中，底物结合实验表明，这两个催化无活性的突变体对葡萄糖具有高亲和力，并且观察到野生型AtHXK1存在有序的底物结合机制。分别以1.8 Å和2.0 Å的分辨率测定了AtHXK1处于无活性未结合配体形式和活性葡萄糖结合形式的结构。这些结构揭示了葡萄糖结合后AtHXK1的结构域重排。葡萄糖结合形式的AtHXK1(S177A)的2.1 Å分辨率结构显示出与野生型相似的葡萄糖结合相互作用。基于这些结构提出了一个葡萄糖感知网络。综上所述，这些结果为AtHXK1的双重功能提供了结构上的解释。
