Department of Structural Biology, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15260, USA.
J Biol Chem. 2010 Apr 23;285(17):13057-65. doi: 10.1074/jbc.M109.094938. Epub 2010 Feb 10.
Cyanovirin-N (CV-N) is a two-domain, cyanobacterial protein that inhibits human immunodeficiency virus (HIV) at nanomolar concentrations by binding to high mannose sugars on the HIV envelope glycoprotein gp120. The wild type protein can exist as a monomer or a domain-swapped dimer with the monomer and dimer containing two or four sugar binding sites, respectively, one on each domain. Here we demonstrate that monomeric, single binding site mutants are completely inactive and that a single site, whether located on domain A or B, is insufficient to impart the antiviral activity. Linking inactive, monomeric proteins in a head-to-head fashion by an intermolecular disulfide bond or by creating an exclusively domain-swapped dimer via a hinge residue deletion restored antiviral activity to levels similar to that of wild type CV-N. These findings demonstrate unequivocally that multisite binding by CV-N type lectins is necessary for viral inhibition.
Cyanovirin-N (CV-N) 是一种两结构域蓝藻蛋白，以纳摩尔浓度抑制人类免疫缺陷病毒 (HIV)，通过与 HIV 包膜糖蛋白 gp120 上的高甘露糖结合。野生型蛋白可以以单体或结构域交换二聚体形式存在，单体和二聚体分别含有两个或四个糖结合位点，每个结构域各一个。本文中我们证明，单体、单结合位点突变体完全无活性，而且一个结合位点，无论是位于结构域 A 还是 B，都不足以赋予抗病毒活性。通过分子间二硫键将无活性的单体蛋白以头对头的方式连接，或者通过铰链残基缺失创建仅结构域交换的二聚体，恢复抗病毒活性至与野生型 CV-N 相似的水平。这些发现明确表明，CV-N 型凝集素的多位点结合对于病毒抑制是必需的。
