Huwa Nikolai, Weiergräber Oliver H, Kirsch Christian, Schaffrath Ulrich, Classen Thomas
Institute for Bio- and Geosciences 1: Bioorganic Chemistry, Forschungszentrum Jülich, 52425 Jülich, Germany.
Institute of Biological Information Processing 7: Structural Biochemistry, and JuStruct, Forschungszentrum Jülich, 52425 Jülich, Germany.
Int J Mol Sci. 2021 May 26;22(11):5639. doi: 10.3390/ijms22115639.
The monocot chimeric jacalin OsJAC1 from consists of a dirigent and a jacalin-related lectin domain. The corresponding gene is expressed in response to different abiotic and biotic stimuli. However, there is a lack of knowledge about the basic function of the individual domains and their contribution to the physiological role of the entire protein. In this study, we have established a heterologous expression in with high yields for the full-length protein OsJAC1 as well as its individual domains. Our findings showed that the secondary structure of both domains is dominated by β-strand elements. Under reducing conditions, the native protein displayed clearly visible transition points of thermal unfolding at 59 and 85 °C, which could be attributed to the lectin and the dirigent domain, respectively. Our study identified a single carbohydrate-binding site for each domain with different specificities towards mannose and glucose (jacalin domain), and galactose moieties (dirigent domain), respectively. The recognition of different carbohydrates might explain the ability of OsJAC1 to respond to different abiotic and biotic factors. This is the first report of specific carbohydrate-binding activity of a DIR domain, shedding new light on its function in the context of this monocot chimeric jacalin.
来自单子叶植物的嵌合jacalin蛋白OsJAC1由一个 dirigent结构域和一个jacalin相关凝集素结构域组成。相应的基因在不同的非生物和生物刺激下表达。然而，关于各个结构域的基本功能及其对整个蛋白质生理作用的贡献，我们还缺乏了解。在本研究中，我们已在[具体表达系统]中实现了全长蛋白OsJAC1及其各个结构域的高产异源表达。我们的研究结果表明，两个结构域的二级结构均以β-链元件为主。在还原条件下，天然蛋白在59℃和85℃时显示出明显可见的热解折叠转变点，这分别可归因于凝集素结构域和dirigent结构域。我们的研究为每个结构域确定了一个单一的碳水化合物结合位点，它们分别对甘露糖和葡萄糖（jacalin结构域）以及半乳糖部分（dirigent结构域）具有不同的特异性。对不同碳水化合物的识别可能解释了OsJAC1对不同非生物和生物因子作出反应的能力。这是关于DIR结构域特异性碳水化合物结合活性的首次报道，为其在这种单子叶植物嵌合jacalin中的功能提供了新的线索。
