Abstract

Arundo donax lectin (ADL) is a 170 amino acid protein that can be purified from the rhizomes of the giant reed or giant cane by exploiting its selective binding to chitin followed by elution with N-acetylglucosamine. The lectin is listed in the UniProt server, the largest protein sequence database, as an uncharacterized protein with chitin-binding domains (A0A0A9P802). This paper reports the purification, structure and ligand-binding properties of ADL. The lectin is a homodimer in which the two protomers are linked by two disulfide bridges. Each polypeptide chain presents four carbohydrate-binding modules that belong to carbohydrate-binding module family 18. A high degree of sequence similarity is observed among the modules present in each protomer. We have determined the X-ray structure of the apo-protein to a resolution of 1.70 Å. The carbohydrate-binding modules, that span a sequence of approximately 40 amino acids, present four internal disulfide bridges, a very short antiparallel central beta sheet and three short alpha helices, two on one side of the beta sheet and one on the other. The structures of the complexes of the lectin with N-acetylglucosamine, N-acetyllactosamine, N-acetylneuraminic acid and N-N’diacetylchitobiose reveal that ADL has two primary and two secondary carbohydrate-binding sites per dimer. They are located at the interface between the two protomers, and each binding site involves residues of both chains. The lectin presents structural similarity to the wheat germ agglutinin family, in particular, to isoform 3.

中文翻译：

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大芦苇 (Arundo donax) 凝集素 (ADL) 的结构和特性

摘要

Arundo donax凝集素 (ADL) 是一种 170 个氨基酸的蛋白质，可通过利用其与几丁质的选择性结合，然后用N-乙酰氨基葡萄糖。凝集素在最大的蛋白质序列数据库 UniProt 服务器中被列为具有几丁质结合结构域 (A0A0A9P802) 的未表征蛋白质。本文报道了 ADL 的纯化、结构和配体结合特性。凝集素是同型二聚体，其中两个原体通过两个二硫键连接。每条多肽链呈现四个碳水化合物结合模块，属于碳水化合物结合模块家族 18。在每个原聚体中存在的模块之间观察到高度的序列相似性。我们已确定载脂蛋白的 X 射线结构，分辨率为 1.70 Å。跨越约 40 个氨基酸序列的碳水化合物结合模块具有四个内部二硫键、一个非常短的反平行中心 β 折叠和三个短 α 螺旋，两个在测试表的一侧，一个在另一侧。凝集素配合物的结构N-乙酰氨基葡萄糖、 N-乙酰乳糖胺、 N-乙酰神经氨酸和N - N '二乙酰壳二糖表明ADL每个二聚体具有两个初级和两个次级碳水化合物结合位点。它们位于两个原体之间的界面，每个结合位点都涉及两条链的残基。凝集素与小麦胚芽凝集素家族，特别是同种型 3 具有结构相似性。