Takeda Shuichi, Saitoh Akihiko, Furuta Mayumi, Satomi Nao, Ishino Atsushi, Nishida Gakushi, Sudo Hiroaki, Hotani Hirokazu, Takiguchi Kingo
Department of Molecular Biology, School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
J Mol Biol. 2006 Sep 22;362(3):403-13. doi: 10.1016/j.jmb.2006.07.071. Epub 2006 Aug 1.
The destabilization of vesicles caused by interactions between lipid bilayers and proteins was studied by direct, real-time observation using high-intensity dark-field microscopy. We previously reported that talin, a cytoskeletal submembranous protein, can reversibly open stable large holes in giant liposomes made of neutral and acidic phospholipids. Talin and other proteins belonging to the band 4.1 superfamily have the FERM domain at their N-terminal and interact with lipid membranes via that domain. Here, we observed that band 4.1, ezrin and moesin, members of the band 4.1 superfamily, are also able to open stable holes in liposomes. However, truncation of their C-terminal domains, which can interact with the N-terminal FERM domain, impaired their hole opening activities. Oligomeric states of ezrin affected the capability of the membrane hole formation. Phosphatidylinositol bisphosphate (PIP2), which binds to the FERM domain and disrupts the interaction between the N and C termini of the band 4.1 superfamily, down-regulates their membrane opening activity. These results suggest that the intermolecular interaction plays a key role in the observed membrane hole formation.
利用高强度暗场显微镜进行直接实时观察，研究了脂质双层与蛋白质之间相互作用导致的囊泡不稳定现象。我们之前报道过，一种细胞骨架膜下蛋白——踝蛋白，能够可逆地在由中性和酸性磷脂制成的巨型脂质体中打开稳定的大洞。踝蛋白以及其他属于4.1带超家族的蛋白质在其N端具有FERM结构域，并通过该结构域与脂质膜相互作用。在此，我们观察到4.1带超家族的成员4.1带蛋白、埃兹蛋白和膜突蛋白也能够在脂质体中打开稳定的孔。然而，它们与N端FERM结构域相互作用的C端结构域的截短会损害其开孔活性。埃兹蛋白的寡聚状态影响膜孔形成的能力。与FERM结构域结合并破坏4.1带超家族N端和C端之间相互作用的磷脂酰肌醇二磷酸（PIP2）会下调它们的膜开孔活性。这些结果表明分子间相互作用在观察到的膜孔形成中起关键作用。
