Carbohydrate recognition by a large sialidase toxin from Clostridium perfringenis
Carbohydrate recognition by a large sialidase toxin from Clostridium perfringenis
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DOI：
10.1021/bi701317g
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发表时间：
2007-10-09
期刊：
影响因子：
2.9
通讯作者：
HealeyT, Michael
中科院分区：
文献类型：
--
作者：
Boraston, Alisdair B.;Ficko-Blean, Elizabeth;HealeyT, Michael
产气荚膜梭菌的肌坏死分离株分泌多模块唾液酸酶，通常称为“大唾液酸酶”，其有助于该细菌的毒力。NanJ是两种分泌型L唾液酸酶中最大的，具有1173个氨基酸，并且包含6个不同的模块，从N-末端开始，它们是家族32碳水化合物结合模块（CBM）、家族40 CBM、家族33糖苷水解酶、未知功能的模块、未知功能的家族82“X-模块”和与纤连蛋白III型结构域具有氨基酸相似性的模块。梭菌唾液酸酶的水解酶活性是相当有据可查的，然而，其附属结构域的功能是完全未调查的。在此，我们描述了分离的家族32 CBM（CBM 32）和分离的家族40 CBM（CBM 40）的碳水化合物结合活性。CBM 32显示结合半乳糖或N-乙酰半乳糖胺，而CBM 40是唾液酸特异性的，尽管两种CBM似乎以非常低的亲和力结合。在2.25埃与半乳糖的复合物中测定了CBM 32的晶体结构。这揭示了似乎是一个非常简单的半乳糖结合位点。在2.20埃下测定了与含有唾液酸的分子复合的CBM 40的晶体结构，该分子偶然与CBM 40结晶，揭示了CBM 40-唾液酸相互作用的分子细节。总体而言，结果表明NanJ含有碳水化合物特异性结合模块，其功能可能是将酶靶向具有混合聚糖群的分子或细胞，所述聚糖群终止于半乳糖/N-乙酰半乳糖胺或唾液酸。
Myonecrotic isolates of Clostridium perfringens secrete multimodular sialidases, often termed "large sialidases", that contribute to the virulence of this bacterium. NanJ is the largest of the two secreted L sialidases at 1173 amino acids and comprises 6 different modules which are, from the N-terminus, a family 32 carbohydrate binding module (CBM), a family 40 CBM, a family 33 glycoside hydrolase, a module of unknown function, a family 82 "X-module" of unknown function, and a module with amino acid similarity to fibronectin type III domains. The hydrolase activity of clostridial sialidases is quite well documented; however, the functions of their accessory domains are entirely uninvestigated. Here we describe the carbohydrate binding activity of the isolated family 32 CBM (CBM32) and the isolated family 40 CBM (CBM40). CBM32 is shown to bind galactose or N-acetylgalactosamine, while CBM40 is sialic acid specific, though both CBMs appear to bind with very low affinities. The crystal structure of CBM32 was determined at 2.25 angstrom in complex with galactose. This revealed what appears to be a very simple galactose binding site. The crystal structure of CBM40 was determined at 2.20 angstrom in complex with a sialic acid containing molecule that it fortuitously crystallized with, revealing the molecular details of the CBM40-sialic acid interaction. Overall, the results indicate that NanJ contains carbohydrate specific binding modules that likely function to target the enzyme to molecules or cells bearing mixed populations of glycans that terminate in either galactose/N-acetylgalactosamine or sialic acid.