Many viruses destabilize cellular membranous compartments to form their replication complexes, but the mechanism(s) underlying membrane perturbation remains unknown. Expression in eukaryotic cells of NS4B, a protein of the hepatitis C virus (HCV), alters membranous complexes and induces structures similar to the so-called membranous web that appears crucial to the formation of the HCV replication complex. As over-expression of the protein is lethal to both prokaryotic and eukaryotic cells, NS4B was produced in large quantities in a “cell-free” system in the presence of detergent, after which it was inserted into lipid membranes. X-ray diffraction revealed that NS4B modifies the phase diagram of synthetic lipid aqueous phases considerably, perturbing the transition temperature and cooperativity. Cryo-electron microscopy demonstrated that NS4B introduces significant disorder in the synthetic membrane as well as discontinuities that could be interpreted as due to the formation of pores and membrane merging events.

C- and N-terminal fragments of NS4B are both able to destabilize liposomes. While most NS4B amphipathic peptides perforate membranes, one NS4B peptide induces membrane fusion. Cryo-electron microscopy reveals a particular structure that can be interpreted as arising from hemi-fusion-like events. Amphipathic domains are present in many proteins, and if exposed to the aqueous cytoplasmic medium are sufficient to destabilize membranes in order to form viral replication complexes. These domains have important functions in the viral replication cycle, and thus represent potential targets for the development of anti-viral molecules.

许多病毒破坏细胞膜隔室的稳定性以形成其复制复合物，但膜微扰的潜在机制仍然未知。NS4B（丙型肝炎病毒（HCV）的一种蛋白质）在真核细胞中的表达会改变膜状复合物，并诱导类似于所谓的膜状网的结构，这种结构对HCV复制复合物的形成至关重要。由于蛋白质的过表达对原核和真核细胞都具有致命性，因此在存在去污剂的情况下，在“无细胞”系统中大量产生了NS4B，然后将其插入脂质膜。X射线衍射表明，NS4B极大地改变了合成脂质水相的相图，干扰了转变温度和协同性。

NS4B的C和N末端片段都能够使脂质体不稳定。虽然大多数NS4B两亲性肽会穿透膜，但一种NS4B肽会诱导膜融合。低温电子显微镜揭示了一种特殊的结构，该结构可以解释为源于半融合样事件。两亲性结构域存在于许多蛋白质中，并且如果暴露于水性细胞质介质中，足以使膜不稳定，从而形成病毒复制复合物。这些结构域在病毒复制周期中具有重要功能，因此代表了抗病毒分子发展的潜在靶标。