Structural basis of a fungal galectin from Agrocybe cylindracea for recognizing sialoconjugate
Structural basis of a fungal galectin from Agrocybe cylindracea for recognizing sialoconjugate
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DOI：
10.1016/j.jmb.2005.06.045
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发表时间：
2005-08-26
影响因子：
5.6
通讯作者：
Yagi, F
中科院分区：
文献类型：
--
作者：
Ban, M;Yoon, HJ;Yagi, F
来自食用真菌茶树菇 (ACG) 的半乳糖凝集素对 N-乙酰神经氨酰乳糖 (NeuAc α 2-3 乳糖) 有强烈的偏好。通过对无配体的ACG及其与乳糖、3'-磺酰乳糖和NeuAc α 2-3乳糖的复合物进行X射线晶体分析，探讨了ACG的糖识别机制。精细结构表明，ACG 是一种“原始”型半乳糖凝集素，由两个反向平行片材的 β-三明治组成，每个片材有 6 条链，与动物半乳糖素的 5 条链和 6 条链相反。溶液中的ACG二聚体被归类为“层”型。该半乳糖凝集素的碳水化合物识别结构域 (CRD) 与动物半乳糖凝集素相同，只是替换了一个残基 Ala64，该残基对应于人半乳糖凝集素 1 中的 Asn46。ACG 中涉及 Ser44 和 Asn46 的 5 个残基插入改变了糖结合位点的结构，从而提供了唾液酸特异性。此外，发现在无配体形式的CRD附近的硫酸根离子的结合导致由Ser44和Pro45之间的主链顺式/反式转变引起的环区构象的变化。 (c) 2005 Elsevier Ltd. 保留所有权利。
Galectin from an edible fungus Agrocybe cylindracea (ACG) has a strong preference for N-acetylneuraminyl lactose (NeuAc alpha 2-3lactose). The sugar recognition mechanism of ACG was explored by the X-ray crystallographic analyses of ligand-free ACG, and its complex with lactose, 3'-sulfonyl lactose and NeuAc alpha 2-3lactose. The refined structure shows that ACG is a "proto"-type galectin composed of beta-sanclwich of two antiparallel sheets, each with six strands, in contrast to the five and six strands in animal galectins. ACG dimer in solution was classified as being among the "layer"-type. The carbohydrate recognition domain (CRD) of this galectin is common to those of animal galectins, except for substitution of one residue, Ala64, which corresponds to Asn46 in human galectin 1. A five-residue insertion in ACG at positions 42-46 involving Ser44 and Asn46 modified the architecture of the sugar binding site that contributes sialic acid specificity. Furthermore, it was found that the binding of a sulfate ion near the CRD in the ligand-free form led to a change in the conformation of the loop region caused by main-chain cis/trans transition between Ser44 and Pro45. (c) 2005 Elsevier Ltd. All rights reserved.