Amphiphilic proteins coassemble into multiphasic condensates and act as biomolecular surfactants.
Amphiphilic proteins coassemble into multiphasic condensates and act as biomolecular surfactants.
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两亲性蛋白质共组装成多相缩合物并充当生物分子表面活性剂。
DOI：
10.1073/pnas.2109967118
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发表时间：
2021
影响因子：
11.1
通讯作者：
Schuster,BenjaminS
中科院分区：
文献类型：
--
作者：
Kelley,FleurieM;Favetta,Bruna;Regy,RoshanMammen;Mittal,Jeetain;Schuster,BenjaminS
细胞含有无膜区室，其由于液-液相分离而组装，包括具有复杂形态的生物分子缩合物。例如，某些浓缩物被不同组成的膜包围，例如Ape 1浓缩物被一层Atg 19包裹，这是酵母中选择性自噬所需的。其他缩合物是多相的，具有不同组成和功能的嵌套液相，例如在核仁中的核糖体生物合成的情况下。必须调节这种冷凝物的大小和结构以实现适当的生物功能。我们利用生物启发的方法来发现两亲性表面活性剂样蛋白质如何有助于生物分子缩合物的结构和大小调节。我们设计并研究了两亲性蛋白家族，包括一个相分离结构域和一个非相分离结构域。特别是，这些蛋白质含有可溶性结构域谷胱甘肽S-转移酶（GST）或麦芽糖结合蛋白（MBP），融合到来自P颗粒蛋白LAF-1的固有无序RGG结构域。当一种两亲性蛋白质与RGG-RGG在体外混合时，蛋白质组装成有包膜的缩合物，其中RGG-RGG位于核心，而两亲性蛋白质形成表面膜层。重要的是，我们发现基于MBP的两亲物是表面活性剂，并且影响液滴尺寸，随着表面活性剂浓度的增加，液滴半径变小。相比之下，GST为基础的两亲物在增加的浓度与RGG-RGG共组装成多相结构。我们提出了一个机制，这些实验观察，支持分子模拟的最低限度的模型。我们推测，表面活性剂蛋白可能在调节生物分子凝聚物的结构和功能方面发挥重要作用。
Cells contain membraneless compartments that assemble due to liquid–liquid phase separation, including biomolecular condensates with complex morphologies. For instance, certain condensates are surrounded by a film of distinct composition, such as Ape1 condensates coated by a layer of Atg19, required for selective autophagy in yeast. Other condensates are multiphasic, with nested liquid phases of distinct compositions and functions, such as in the case of ribosome biogenesis in the nucleolus. The size and structure of such condensates must be regulated for proper biological function. We leveraged a bioinspired approach to discover how amphiphilic, surfactant-like proteins may contribute to the structure and size regulation of biomolecular condensates. We designed and examined families of amphiphilic proteins comprising one phase-separating domain and one non–phase-separating domain. In particular, these proteins contain the soluble structured domain glutathione S-transferase (GST) or maltose binding protein (MBP), fused to the intrinsically disordered RGG domain from P granule protein LAF-1. When one amphiphilic protein is mixed in vitro with RGG-RGG, the proteins assemble into enveloped condensates, with RGG-RGG at the core and the amphiphilic protein forming the surface film layer. Importantly, we found that MBP-based amphiphiles are surfactants and influence droplet size, with increasing surfactant concentration resulting in smaller droplet radii. In contrast, GST-based amphiphiles at increased concentrations coassemble with RGG-RGG into multiphasic structures. We propose a mechanism for these experimental observations, supported by molecular simulations of a minimalist model. We speculate that surfactant proteins may play a significant role in regulating the structure and function of biomolecular condensates.