The N-terminal Helical Region of the Hepatitis C Virus p7 Ion Channel Protein Is Critical for Infectious Virus Production

The hepatitis C virus (HCV) p7 protein is required for infectious virus production via its role in assembly and ion channel activity. Although NMR structures of p7 have been reported, the location of secondary structural elements and orientation of the p7 transmembrane domains differ among models. Furthermore, the p7 structure-function relationship remains unclear. Here, extensive mutagenesis, coupled with infectious virus production phenotyping and molecular modeling, demonstrates that the N-terminal helical region plays a previously underappreciated yet critical functional role, especially with respect to E2/p7 cleavage efficiency. Interrogation of specific N-terminal helix residues identified as having p7-specific defects and predicted to point toward the channel pore, in a context of independent E2/p7 cleavage, further supports p7 as a structurally plastic, minimalist ion channel. Together, our findings indicate that the p7 N-terminal helical region is critical for E2/p7 processing, protein-protein interactions, ion channel activity, and infectious HCV production.丙型肝炎病毒（hepatitis C virus, HCV）p7蛋白通过参与病毒组装与离子通道活性，是产生感染性病毒颗粒的必需因子。尽管已有p7蛋白的核磁共振（nuclear magnetic resonance, NMR）结构被报道，但不同模型中p7的二级结构元件位置与跨膜结构域取向均存在差异。此外，p7蛋白的结构-功能关系仍未明确。本研究通过大规模诱变结合感染性病毒产生表型分析与分子建模，证实p7蛋白的N端螺旋区域发挥着此前未被充分重视的关键功能作用，尤其体现在E2/p7切割效率方面。在E2/p7独立切割的背景下，对经鉴定存在p7特异性缺陷且被预测指向通道孔道的特定N端螺旋残基进行分析，进一步佐证p7是一种结构具有可塑性的极简离子通道。综上，本研究结果表明，p7蛋白的N端螺旋区域对于E2/p7蛋白加工、蛋白质-蛋白质相互作用、离子通道活性以及感染性HCV的产生均具有关键作用。