Structure and ligand binding of carbohydrate-binding module CsCBM6-3 reveals similarities with fucose-specific lectins and "galactose-binding" domains
Structure and ligand binding of carbohydrate-binding module CsCBM6-3 reveals similarities with fucose-specific lectins and "galactose-binding" domains
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DOI：
10.1016/s0022-2836(03)00152-9
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发表时间：
2003-03-28
影响因子：
5.6
通讯作者：
Davies, G
中科院分区：
文献类型：
--
作者：
Boraston, AB;Notenboom, V;Davies, G
碳水化合物结合多肽，包括来自多糖酶的碳水化合物结合模块（CBM）和凝集素，在自然界中广泛存在。虽然CBM被传统地认为与凝集素不同，因为它们被发现附加到多糖降解酶上，但这种区别是模糊的。CsCBM 6 -3（来自粪梭菌的木聚糖酶中的“序列家族6”CBM）在2.3埃下的晶体结构揭示了与来自MvX 56（在来自绿色小单孢菌的家族33糖苷水解酶唾液酸酶中发现的模块）和来自欧洲鳗的凝集素AAA相似的全β折叠。序列分析将MvX 56和AAA分类为与含有CsCBM 6 -3的家族不同的家族。虽然这些多肽在结构上相似，但它们具有完全不同的碳水化合物结合特异性。已知AAA结合岩藻糖; CsCBM 6 -3结合纤维素、木聚糖和其他β-葡聚糖。在这里，我们证明了MvX 56结合半乳糖，乳糖和唾液酸。CsCBM 6 -3与木三糖、纤维二糖和昆布二糖复合的晶体结构（分辨率分别为2.0埃、1.35埃和1.0埃）显示CsCBM 6 -3的结合位点位于与MvX 56和AAA相同的多肽面上。配体结合表面的细微差异引起了不同的特异性和生物活性，进一步模糊了经典凝集素和CBM之间的区别。(C)2003爱思唯尔科技有限公司版权所有。
Carbohydrate-binding polypeptides, including carbohydrate-binding modules (CBMs) from polysaccharidases, and lectins, are widespread in nature. Whilst CBMs are classically considered distinct from lectins, in that they are found appended to polysaccharide-degrading enzymes, this distinction is blurring. The crystal structure of CsCBM6-3, a "sequence-family 6" CBM in a xylanase from Clostridium stercorarium, at 2.3 Angstrom reveals a similar, all beta-sheet fold to that from MvX56, a module found in a family 33 glycoside hydrolase sialidase from Micromonospora viridifaciens, and the lectin AAA from Anguilla anguilla. Sequence analysis leads to the classification of MvX56 and AAA into a family distinct from that containing CsCBM6-3. Whilst these polypeptides are similar in structure they have quite different carbohydrate-binding specificities. AAA is known to bind fucose; CsCBM6-3 binds cellulose, xylan and other beta-glucans. Here we demonstrate that MvX56 binds galactose, lactose and sialic acid. Crystal structures of CsCBM6-3 in complex with xylotriose, cellobiose, and laminaribiose, 2.0 Angstrom, 1.35 Angstrom, and 1.0 Angstrom resolution, respectively, reveal that the binding site of CsCBM6-3 resides on the same polypeptide face as for MvX56 and AAA. Subtle differences in the ligand-binding surface give rise to the different specificities and biological activities, further blurring the distinction between classical lectins and CBMs. (C) 2003 Elsevier Science Ltd. All rights reserved.