当前的H1N1流感病毒对成熟的抗病毒药物金刚胺和金刚乙胺有抵抗力。这两种药物以M2蛋白为作用目标，该蛋白是一种多功能跨膜质子通道。这个通道的结构一直是一个有些争议的话题，因为M2通道一部分的X-射线晶体结构所显示的电子密度相应于微孔N-端那一部分的单一金刚胺分子，而该通道更大一部分的溶液NMR结构则显示有四个金刚乙胺分子结合到螺旋体C-端朝向类脂的表面上。
现在，随着处在一个磷脂双层中的M2通道的高分辨率结构（该结构利用固态NMR光谱获得）的发表，这个问题似乎已经解决。该结构显示金刚胺有两个结合点：N-端通道腔中一个高亲和度点和C-端蛋白表面上一个低亲和度点。这项工作对于新兴抗流感药物的开发可能会有价值（这是一个重要目标，因为2009年的季节性流感病毒对金刚胺是敏感的，但对“达菲”（Tamiflu）却有抵抗力），这便提出一个可能性：将来可能会出现多种抗药性病毒类型。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 463, 689-692 (4 February 2010) | doi:10.1038/nature08722
Structure of the amantadine binding site of influenza M2 proton channels in lipid bilayers
Sarah D. Cady1, Klaus Schmidt-Rohr1, Jun Wang2, Cinque S. Soto2, William F. DeGrado2 & Mei Hong1
1 Department of Chemistry, Iowa State University, Ames, Iowa 50011 2, USA
2 Department of Biochemistry & Biophysics, School of Medicine, and Department of Chemistry University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059, USA
The M2 protein of influenza A virus is a membrane-spanning tetrameric proton channel targeted by the antiviral drugs amantadine and rimantadine1. Resistance to these drugs has compromised their effectiveness against many influenza strains, including pandemic H1N1. A recent crystal structure of M2(22–46) showed electron densities attributed to a single amantadine in the amino-terminal half of the pore2, indicating a physical occlusion mechanism for inhibition. However, a solution NMR structure of M2(18–60) showed four rimantadines bound to the carboxy-terminal lipid-facing surface of the helices3, suggesting an allosteric mechanism. Here we show by solid-state NMR spectroscopy that two amantadine-binding sites exist in M2 in phospholipid bilayers. The high-affinity site, occupied by a single amantadine, is located in the N-terminal channel lumen, surrounded by residues mutated in amantadine-resistant viruses. Quantification of the protein–amantadine distances resulted in a 0.3??-resolution structure of the high-affinity binding site. The second, low-affinity, site was observed on the C-terminal protein surface, but only when the drug reaches high concentrations in the bilayer. The orientation and dynamics of the drug are distinct in the two sites, as shown by 2H NMR. These results indicate that amantadine physically occludes the M2 channel, thus paving the way for developing new antiviral drugs against influenza viruses. The study demonstrates the ability of solid-state NMR to elucidate small-molecule interactions with membrane proteins and determine high-resolution structures of their complexes.
