Solution structure of a cyanovirin-N:Manα1-2Manα complex:: Structural basis for high-affinity carbohydrate-mediated binding to gp120
Solution structure of a cyanovirin-N:Manα1-2Manα complex:: Structural basis for high-affinity carbohydrate-mediated binding to gp120
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DOI：
10.1016/s0969-2126(01)00653-0
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发表时间：
2001-10-01
期刊：
影响因子：
5.7
通讯作者：
Bewley, CA
中科院分区：
文献类型：
--
作者：
Bewley, CA
背景：Cyanovirin-N (CVN) 是一种新型 11 kDa 蓝藻蛋白，可通过与病毒包膜糖蛋白 gp120 的高亲和力碳水化合物介导的相互作用，有效抑制多种 HIV 病毒株的病毒进入。 CVN 包含两个不同亲和力的对称相关碳水化合物结合位点，以纳摩尔亲和力选择性结合 Man(8) D1 D3 和 Man(9)，这些碳水化合物也介导 CVN:gp120 结合。 CVN 与代表性寡糖复合物的高分辨率结构研究对于了解这种前所未有的特异性的结构基础是必要的。结果：我们通过多维异核 NMR 光谱确定了 CVN 与二糖 Man α1-2Man α 的两个等价物复合物的三维溶液结构，Man α1-2Man α 是一种高亲和力配体，代表 Man(8) D1 D3 和 Man(9) 中存在的末端可接近的二糖。该结构揭示了结合的二糖采用堆叠构象，从而解释了 Mans D1 D3 和 Man(9) 相对于其他寡甘露糖结构的选择性，并提出了两个新的碳水化合物结合位点，解释了这两个位点的不同亲和力。高亲和力位点包括几乎包围二糖的深袋，而低亲和力位点包括部分包围二糖的半圆形裂缝。两个结合位点的类似40埃的间距为CVN:gp120结合提供了一个简单的模型。结论：CVN:Man alpha1-2Man alpha。该复合物提供了第一个具有纳摩尔亲和力的甘露糖特异性蛋白质-碳水化合物复合物的高分辨率结构，并呈现出一种新的碳水化合物结合基序，以及一类新的碳水化合物结合蛋白，可促进通过单体蛋白的二价结合。
Background: Cyanovirin-N (CVN) is a novel, 11 kDa cyanobacterial protein that potently inhibits viral entry by diverse strains of HIV through high-affinity carbohydrate-mediated interactions with the viral envelope glycoprotein gp120. CVN contains two symmetry-related carbohydrate binding sites of differing affinities that selectively bind to Man(8) D1 D3 and Man(9) with nanomolar affinities, the carbohydrates that also mediate CVN:gp120 binding. High-resolution structural studies of CVN in complex with a representative oligosaccharide are desirable for understanding the structural basis for this unprecedented specificity.Results: We have determined by multidimensional heteronuclear NMR spectroscopy the three-dimensional solution structure of CVN in complex with two equivalents of the disaccharide Man alpha1-2Man alpha, a high-affinity ligand which represents the terminal-accessible disaccharide present in Man(8) D1 D3 and Man(9). The structure reveals that the bound disaccharide adopts the stacked conformation, thereby explaining the selectivity for Mans D1 D3 and Man(9) over other oligomannose structures, and presents two novel carbohydrate binding sites that account for the differing affinities of the two sites. The high-affinity site comprises a deep pocket that nearly envelops the disaccharide, while the lower-affinity site comprises a semicircular cleft that partially surrounds the disaccharide. The similar to 40 Angstrom spacing of the two binding sites provides a simple model for CVN:gp120 binding.Conclusions: The CVN:Man alpha1-2Man alpha. complex provides the first high-resolution structure of a mannose-specific protein-carbohydrate complex with nanomolar affinity and presents a new carbohydrate binding motif, as well as a new class of carbohydrate binding protein, that facilitates divalent binding via a monomeric protein.