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首页> 外文期刊>Journal of Molecular Biology >Insights into carbohydrate recognition by Narcissus pseudonarcissus lectin: the crystal structure at 2 A resolution in complex with alpha1-3 mannobiose.
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Insights into carbohydrate recognition by Narcissus pseudonarcissus lectin: the crystal structure at 2 A resolution in complex with alpha1-3 mannobiose.

机译：水仙假水仙凝集素对碳水化合物识别的见解：与α1-3甘露二糖复合的2 A分辨率的晶体结构。

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摘要

Carbohydrate recognition by monocot mannose-binding lectins was studied via the crystal structure determination of daffodil (Narcissus pseudonarcissus) lectin. The lectin was extracted from daffodil bulbs, and crystallised in the presence of alpha-1,3 mannobiose. Molecular replacement methods were used to solve the structure using the partially refined model of Hippeastrum hybrid agglutinin as a search model. The structure was refined at 2.0 A resolution to a final R -factor of 18.7 %, and Rfreeof 26.7 %.The main feature of the daffodil lectin structure is the presence of three fully occupied binding pockets per monomer, arranged around the faces of a triangular beta-prism motif. The pockets have identical topology, and can bind mono-, di- or oligosaccharides. Strand exchange forms tightly bound dimers, and higher aggregation states are achieved through hydrophobic patches on the surface, completing a tetramer with internal 222-symmetry. There are therefore 12 fully occupied binding pockets per tetrameric cluster. The tetramer persists in solution, as shown with small-angle X-ray solution scattering. Extensive sideways and out-of-plane interactions between tetramers, some mediated via the ligand, make up the bulk of the lattice contacts.A fourth binding site was also observed. This is unique and has not been observed in similar structures. The site is only partially occupied by a ligand molecule due to the much lower binding affinity. A comparison with the Galanthus nivalis agglutinin/mannopentaose complex suggests an involvement of this site in the recognition mechanism for naturally occurring glycans. Copyright 1999 Academic Press.
机译：通过水仙花（Narcissus pseudonarcissus）凝集素的晶体结构测定研究了单子叶植物甘露糖结合凝集素对碳水化合物的识别。从水仙花球茎中提取凝集素，并在α-1，3甘露二糖存在下结晶。使用分子替代方法来解决该结构，使用Hippeastrum杂交凝集素的部分精炼模型作为搜索模型。以2.0 A的分辨率精炼结构，最终的R因子为18.7％，Rfree为26.7％。水仙花凝集素结构的主要特征是每个单体存在三个完全占据的结合口袋，围绕三角形的表面排列β-棱镜图案。口袋具有相同的拓扑，可以结合单糖，二糖或寡糖。链交换形成紧密结合的二聚体，并且更高的聚集态通过表面上的疏水斑获得，从而完成具有内部222-对称性的四聚体。因此，每个四聚体簇有12个完全占据的结合口袋。四聚体在溶液中持续存在，如小角度X射线溶液散射所示。四聚体之间广泛的侧向和平面外相互作用（某些是通过配体介导的）构成了大部分晶格接触，还观察到了第四个结合位点。这是独特的，在类似结构中尚未观察到。由于低得多的结合亲和力，该位点仅被配体分子部分占据。与Galanthus nivalis凝集素/甘露半乳糖复合物的比较表明该位点参与了天然聚糖的识别机制。版权所有1999，学术出版社。

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