Structural analysis of a plant fatty acid amide hydrolase provides insights into the evolutionary diversity of bioactive acylethanolamides
Structural analysis of a plant fatty acid amide hydrolase provides insights into the evolutionary diversity of bioactive acylethanolamides
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DOI：
10.1074/jbc.ra118.006672
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发表时间：
2019-05-03
影响因子：
4.8
通讯作者：
Chapman, Kent D.
中科院分区：
文献类型：
--
作者：
Aziz, Mina;Wang, Xiaoqiang;Chapman, Kent D.
N-乙酰乙醇胺(NAE)是一种脂肪酸衍生物，在动物系统中包括已知的内源性大麻信号通路的生物活性代谢物。植物也使用NAE信号，这些生物活性分子通常含有含氧酰基。在这里，我们报道了拟南芥信号终止酶脂肪酸酰胺水解酶(FAAH)在2.1和3.2分辨率下以apo形式和配体结合形式的三维晶体结构。这种植物FAAH结构揭示了与唯一其他可用的FAAH结构(RAT)不同的特征。结构表明，虽然催化残基与哺乳动物酶是保守的，但AtFAAH有一个更开放的底物结合口袋，部分内衬有极性残基。膜结合帽和膜通道的组织结构也有明显的根本区别。根据观察到的底物结合口袋的结构特征，动力学分析表明，AtFAAH有效地利用了未取代和含氧的酰乙醇胺作为底物。此外，对apo和配体结合的AtFAAH结构的比较发现，伴随着配体结合的是三组离散的构象变化，这表明了一种独特的挤压和锁定底物结合机制。利用分子动力学模拟，我们进一步评估了这些构象变化，并注意到apo结构中531-537区域的随机卷曲螺旋的部分展开，但不是以配体结合的形式，这表明该区域可能为底物结合口袋提供可塑性。我们的结论是，植物中活性酰乙醇胺的结构差异部分反映在植物FAAHs的结构和功能性质上。
N-Acylethanolamines (NAEs) are fatty acid derivatives that in animal systems include the well-known bioactive metabolites of the endocannabinoid signaling pathway. Plants use NAE signaling as well, and these bioactive molecules often have oxygenated acyl moieties. Here, we report the three-dimensional crystal structures of the signal-terminating enzyme fatty acid amide hydrolase (FAAH) from Arabidopsis in its apo and ligand-bound forms at 2.1- and 3.2- resolutions, respectively. This plant FAAH structure revealed features distinct from those of the only other available FAAH structure (rat). The structures disclosed that although catalytic residues are conserved with the mammalian enzyme, AtFAAH has a more open substrate-binding pocket that is partially lined with polar residues. Fundamental differences in the organization of the membrane-binding cap and the membrane access channel also were evident. In accordance with the observed structural features of the substrate-binding pocket, kinetic analysis showed that AtFAAH efficiently uses both unsubstituted and oxygenated acylethanolamides as substrates. Moreover, comparison of the apo and ligand-bound AtFAAH structures identified three discrete sets of conformational changes that accompany ligand binding, suggesting a unique squeeze and lock substrate-binding mechanism. Using molecular dynamics simulations, we evaluated these conformational changes further and noted a partial unfolding of a random-coil helix within the region 531-537 in the apo structure but not in the ligand-bound form, indicating that this region likely confers plasticity to the substrate-binding pocket. We conclude that the structural divergence in bioactive acylethanolamides in plants is reflected in part in the structural and functional properties of plant FAAHs.