The membrane sculpting ability of BAR domains has been attributed to the intrinsic curvature of their banana-shaped dimeric structure. However, there is often a mismatch between this intrinsic curvature and the diameter of the membrane tubules generated. I-BAR domains are especially mysterious since they are almost flat but generate high negative membrane curvature. Here, we use atomistic implicit-solvent computer modeling to show that the membrane bending of the IRSp53 I-BAR domain is dictated by its higher oligomeric structure, whose curvature is completely unrelated to the intrinsic curvature of the dimer. Two other I-BARs give similar results, whereas a flat F-BAR sheet develops a concave membrane-binding interface, consistent with its observed positive membrane curvature generation. Laterally interacting helical spirals of I-BAR dimers on tube interiors are stable and have an enhanced binding energy that is sufficient for membrane bending to experimentally observed tubule diameters at a reasonable surface density.

BAR 结构域的膜塑形能力归因于其香蕉形二聚体结构的固有曲率。然而，这种固有曲率与生成的膜管直径之间通常存在不匹配。I-BAR 域特别神秘，因为它们几乎是平坦的，但会产生高的负膜曲率。在这里，我们使用原子隐式溶剂计算机建模来表明 IRSp53 I-BAR 域的膜弯曲是由其较高的寡聚结构决定的，其曲率与二聚体的固有曲率完全无关。其他两个 I-BAR 给出了类似的结果，而平坦的 F-BAR 片形成了一个凹膜结合界面，与其观察到的正膜曲率生成一致。