PDF(Pubmed)
Abstract：
The four-point-one ezrin-radixin-moesin homology (FERM) protein domain is a multifunctional protein-lipid binding site, constituting an integral part of numerous membrane-associated proteins. Its interaction with the lipid phosphatidylinositol-4,5-bisphosphate (PIP2), located at the inner leaflet of eukaryotic plasma membranes, is important for localization, anchorage, and activation of FERM-containing proteins. FERM-PIP2 complexes structurally determined so far exclusively feature a 1:1 binding stoichiometry of protein and lipid, with a few basic FERM residues neutralizing the -4 charge of the bound PIP2. Whether this picture from static crystal structures also applies to the dynamic interaction of FERM domains on PIP2 membranes is unknown. We here quantified the stoichiometry of FERM-PIP2 binding in a lipid bilayer using atomistic molecular dynamics simulations and experiments on solid supported membranes for the FERM domains of focal adhesion kinase and ezrin. In contrast to the structural data, we find much higher average stoichiometries of FERM-PIP2 binding, amounting to 1:3 or 1:4 ratios, respectively. In simulations, the full set of basic residues at the membrane interface, 7 and 15 residues for focal adhesion kinase and ezrin, respectively, engages in PIP2 interactions. In addition, Na ions enter the FERM-membrane binding interface, compensating negative PIP2 charges in case of high charge surpluses from bound PIP2. We propose the multivalent binding of FERM domains to PIP2 in lipid bilayers to significantly enhance the stability of FERM-membrane binding and to render the FERM-membrane linkage highly adjustable.
摘要：
四点一ezrin-radixin-moesin同源性（FERM）蛋白结构域是一个多功能的蛋白质-脂质结合位点，构成许多膜相关蛋白的组成部分。它与磷脂酰肌醇-4,5-双磷酸酯（PIP2）的相互作用，位于真核质膜的内小叶，对本地化很重要，含有FERM的蛋白质的锚定和激活。迄今为止在结构上确定的FERM-PIP2复合物仅具有蛋白质和脂质的1：1结合化学计量，几个碱性FERM残基中和结合的PIP2的-4电荷。来自静态晶体结构的图片是否也适用于FERM结构域在PIP2膜上的动态相互作用尚不清楚。我们在这里量化了FERM-PIP2结合在脂质双层中使用原子分子动力学模拟和固体支持膜上的实验的化学计量,对于粘着斑激酶（FAK）和ezrin的FERM结构域。与结构数据相反，我们发现FERM-PIP2结合的平均化学计量高得多，相当于1:3或1:4的比例，分别。在模拟中,膜界面上的全套基本残留物，FAK和ezrin的7和15个残基，分别,参与PIP2交互。此外,钠离子进入FERM-膜结合界面，在来自结合的PIP2的高电荷过剩的情况下补偿负PIP2电荷。我们提出FERM结构域与脂质双层中的PIP2的多价结合以显着增强FERM-膜结合的稳定性并使FERM-膜连接高度可调。
