Domain formation in a fluid mixed lipid bilayer modulated through binding of the C2 protein motif
Domain formation in a fluid mixed lipid bilayer modulated through binding of the C2 protein motif
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DOI：
10.1021/bi0024299
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发表时间：
2001-04-03
期刊：
影响因子：
2.9
通讯作者：
Biltonen, RL
中科院分区：
文献类型：
--
作者：
Hinderliter, A;Almeida, PFF;Biltonen, RL
脂质结构域在功能膜中的作用和形成机制通常受到有限的关注。基于脂质-脂质和蛋白-脂质相互作用之间的热力学耦合可以导致结构域形成的假设，我们的方法结合了实验脂质双层模型系统和该系统简单模型的蒙特卡罗计算机模拟。实验体系是由磷脂酰胆碱（PC）和磷脂酰丝氨酸（PS）的二元混合物组成的流体双层，含有4%的芘标记阴离子磷脂。在双分子层中加入C2蛋白基序（在真核生物信号转导和细胞运输过程中发现的一种结构域）首先增加然后降低芘荧光的准分子/单体比率。我们解释这意味着蛋白质结合诱导阴离子脂质结构域的形成，直到阴离子脂质被蛋白质饱和。蒙特卡罗模拟在一个晶格上进行，代表脂质双分子层，其中添加了蛋白质。重要的参数是不同的脂质相互作用项和实验推导出的蛋白质-脂质优先相互作用项。模拟结果支持实验结论，并表明PS结构域大小随蛋白浓度的变化存在最大值。因此，脂质-蛋白质偶联是脂质和蛋白质在流体双分子层上聚集的可能机制。这些结构域可能是更大的脂质蛋白簇（“筏”）的前体，在细胞膜水平的信号转导等各种生物过程中可能很重要。
The role and mechanism of formation of lipid domains in a functional membrane have generally received limited attention. Our approach, based on the hypothesis that thermodynamic coupling between lipid-lipid and protein-lipid interactions can lead to domain formation, uses a combination of an experimental lipid bilayer model system and Monte Carlo computer simulations of a simple model of that system. The experimental system is a fluid bilayer composed of a binary mixture of phosphatidylcholine (PC) and phosphatidylserine (PS), containing 4% of a pyrene-labeled anionic phospholipid. Addition of the C2 protein motif (a structural domain found in proteins implicated in eukaryotic signal transduction and cellular trafficking processes) to the bilayer first increases and then decreases the excimer/monomer ratio of the pyrene fluorescence. We interpret this to mean that protein binding induces anionic lipid domain formation until the anionic lipid becomes saturated with protein. Monte Carlo simulations were performed on a lattice representing the lipid bilayer to which proteins were added. The important parameters are an unlike lipid-lipid interaction term and an experimentally derived preferential protein-lipid interaction term. The simulations support the experimental conclusion and indicate the existence of a maximum in PS domain size as a function of protein concentration. Thus, lipid-protein coupling is a possible mechanism for both lipid and protein clustering on a fluid bilayer. Such domains could be precursors of larger lipid-protein clusters ('rafts'), which could be important in various biological processes such as signal transduction at the level of the cell membrane.