Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK.
Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
Biomolecules. 2021 Feb 14;11(2):278. doi: 10.3390/biom11020278.
Biomolecular condensates, which assemble via the process of liquid-liquid phase separation (LLPS), are multicomponent compartments found ubiquitously inside cells. Experiments and simulations have shown that biomolecular condensates with many components can exhibit multilayered organizations. Using a minimal coarse-grained model for interacting multivalent proteins, we investigate the thermodynamic parameters governing the formation of multilayered condensates through changes in protein valency and binding affinity. We focus on multicomponent condensates formed by scaffold proteins (high-valency proteins that can phase separate on their own via homotypic interactions) and clients (proteins recruited to condensates via heterotypic scaffold-client interactions). We demonstrate that higher valency species are sequestered to the center of the multicomponent condensates, while lower valency proteins cluster towards the condensate interface. Such multilayered condensate architecture maximizes the density of LLPS-stabilizing molecular interactions, while simultaneously reducing the surface tension of the condensates. In addition, multilayered condensates exhibit rapid exchanges of low valency proteins in and out, while keeping higher valency proteins-the key biomolecules involved in condensate nucleation-mostly within. We also demonstrate how modulating the binding affinities among the different proteins in a multicomponent condensate can significantly transform its multilayered structure, and even trigger fission of a condensate into multiple droplets with different compositions.
生物分子凝聚物通过液-液相分离 (LLPS) 过程组装，是普遍存在于细胞内的多组分隔室。实验和模拟表明，具有许多组分的生物分子凝聚物可以表现出多层次的组织。我们使用一种用于相互作用多价蛋白质的最小粗粒度模型，通过改变蛋白质价数和结合亲和力来研究控制多层凝聚物形成的热力学参数。我们专注于由支架蛋白（可以通过同型相互作用自身相分离的高价蛋白）和客户（通过异型支架-客户相互作用招募到凝聚物的蛋白质）形成的多组分凝聚物。我们证明，高价物种被隔离在多组分凝聚物的中心，而低价蛋白质则聚集在凝聚物的界面处。这种多层次的凝聚物结构最大限度地提高了 LLPS 稳定分子相互作用的密度，同时降低了凝聚物的表面张力。此外，多层次凝聚物表现出低价蛋白质的快速内外交换，而保持高价蛋白质——参与凝聚核形成的关键生物分子——大部分在内部。我们还展示了如何调节多组分凝聚物中不同蛋白质之间的结合亲和力可以显著改变其多层次结构，甚至引发凝聚物分裂成具有不同组成的多个液滴。
