Nature：丙肝病毒阳离子通道的结构被揭示

丙肝病毒 (HCV) 是肝病和肝癌的一个主要病因。由于没有保护性疫苗，也由于治疗方案仍然有限，寻找新的治疗目标便显得很重要。James Chou及其同事在这篇论文中报告了低聚丙肝病毒“viroporin p7”的结构，是通过NMR谱获得的。该蛋白能自组成一个可传导阳离子的通道复合物。该通道六聚物的一个高分辨率视图显示了新颖的漏斗状通道结构，而功能研究则识别出了对通道活性重要的残体。

英文摘要：

Nature    doi:10.1038/nature12283

Unusual architecture of the p7 channel from hepatitis C virus

Bo OuYang,Shiqi Xie,Marcelo J. Berardi,Xinhao Zhao, Jyoti Dev, Wenjing Yu,Bing Sun  & James J. Chou

The hepatitis C virus (HCV) has developed a small membrane protein, p7, which remarkably can self-assemble into a large channel complex that selectively conducts cations. We wanted to examine the structural solution that the viroporin adopts in order to achieve selective cation conduction, because p7 has no homology with any of the known prokaryotic or eukaryotic channel proteins. The activity of p7 can be inhibited by amantadine and rimantadine, which are potent blockers of the influenza M2 channel and licensed drugs against influenza infections. The adamantane derivatives have been used in HCV clinical trials, but large variation in drug efficacy among the various HCV genotypes has been difficult to explain without detailed molecular structures. Here we determine the structures of this HCV viroporin as well as its drug-binding site using the latest nuclear magnetic resonance (NMR) technologies. The structure exhibits an unusual mode of hexameric assembly, where the individual p7 monomers, i, not only interact with their immediate neighbours, but also reach farther to associate with the i+2 and i+3 monomers, forming a sophisticated, funnel-like architecture. The structure also points to a mechanism of cation selection: an asparagine/histidine ring that constricts the narrow end of the funnel serves as a broad cation selectivity filter, whereas an arginine/lysine ring that defines the wide end of the funnel may selectively allow cation diffusion into the channel. Our functional investigation using whole-cell channel recording shows that these residues are critical for channel activity. NMR measurements of the channel–drug complex revealed six equivalent hydrophobic pockets between the peripheral and pore-forming helices to which amantadine or rimantadine binds, and compound binding specifically to this position may allosterically inhibit cation conduction by preventing the channel from opening. Our data provide a molecular explanation for p7-mediated cation conductance and its inhibition by adamantane derivatives.

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