Laboratory of Biochemistry and Glycobiology, Department of Molecular Biotechnology, Ghent University, Coupure links 653, 9000 Ghent, Belgium.
Biomolecules. 2012 Oct 8;2(4):415-34. doi: 10.3390/biom2040415.
Plants synthesize small amounts of carbohydrate-binding proteins on exposure to stress. For example, on exposure to drought, high salt, wounding and by treatment with some plant hormones or by pathogen attack. In contrast to the 'classical' plant lectins that are mostly located in the vacuolar compartment, this new class of inducible lectins is present in the cytoplasm and in the nucleus. Taking into account that any physiological role of plant lectins most likely relies on their specific carbohydrate-binding activity and specificity, the discovery of these stress-related lectins provides strong evidence for the importance of protein-carbohydrate-interactions in plant cells. Hitherto, six families of such nucleocytoplasmic lectins have been identified in plants. This review will focus on the nucleocytoplasmic lectins with one or more Euonymus lectin (EUL) domain(s). The carbohydrate-binding specificity of EUL proteins from a monocot, a dicot and a lower plant has been compared. Furthermore, modeling of the different EUL domains revealed a similar ß-trefoil fold consisting of three bundles of ß-sheet organized around a pseudo three-fold symmetry axis. Despite the sequence similarity and the conserved amino acids in the binding site, glycan array analyses showed that the EUL domain has a promiscuous carbohydrate-binding site capable of accommodating high mannose N-glycans, blood group B related structures and galactosylated epitopes.
植物在受到胁迫时会合成少量的碳水化合物结合蛋白。例如，在受到干旱、高盐、创伤以及某些植物激素处理或受到病原体攻击时。与主要位于液泡区室中的“经典”植物凝集素不同，这种新的诱导型凝集素存在于细胞质和细胞核中。考虑到植物凝集素的任何生理作用很可能依赖于其特定的碳水化合物结合活性和特异性，这些与应激相关的凝集素的发现为蛋白质-碳水化合物相互作用在植物细胞中的重要性提供了有力证据。迄今为止，已经在植物中鉴定出了六类这样的核质凝集素。这篇综述将重点介绍具有一个或多个卫矛凝集素（EUL）结构域的核质凝集素。比较了单子叶植物、双子叶植物和低等植物中的 EUL 蛋白的碳水化合物结合特异性。此外，对不同 EUL 结构域的建模揭示了相似的 β-三叶折叠结构，由围绕拟三度对称轴排列的三个 β-折叠束组成。尽管存在序列相似性和结合位点中的保守氨基酸，但糖阵列分析表明，EUL 结构域具有一个混杂的碳水化合物结合位点，能够容纳高甘露糖 N-聚糖、血型 B 相关结构和半乳糖化表位。
