Favetta Bruna, Wang Huan, Shi Zheng, Schuster Benjamin S
Department of Biomedical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States.
Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States.
Langmuir. 2025 Sep 9;41(35):23827-23836. doi: 10.1021/acs.langmuir.5c03118. Epub 2025 Aug 27.
Biomolecular condensates are protein-dense regions in cells that often arise from liquid-liquid phase separation. Interfacial tension is a key determinant of biomolecular condensate behavior, influencing condensate size and interactions with intracellular structures. Certain proteins and RNAs are known to selectively localize to the interface of condensates, where they can regulate condensate function in cells. Previously, we designed amphiphilic proteins that preferentially adsorb to the surface of condensates. These proteins contain one condensate-philic domain (RGG) and one condensate-phobic domain (MBP or GST). Here, we demonstrate through direct quantification that these amphiphilic proteins act as surfactants, reducing the interfacial tension of RGG-RGG condensates from ∼260 to ∼100 μN/m in a concentration-dependent manner. Notably, the GST-based surfactant protein exhibits a 10-fold greater efficacy in lowering interfacial tension compared with the MBP-based surfactant. We show that this increased efficacy is due to its higher surface density, driven by GST's ability to oligomerize. We also show that these surfactant proteins slow droplet fusion and reduce the average droplet size, as would be expected of a typical surfactant. Our findings quantitatively show how surfactant proteins can play a critical role in regulating the behavior of biomolecular condensates by modulating their interfacial tension.
生物分子凝聚物是细胞中蛋白质密集的区域，通常由液-液相分离产生。界面张力是生物分子凝聚物行为的关键决定因素，影响凝聚物大小以及与细胞内结构的相互作用。已知某些蛋白质和RNA会选择性地定位于凝聚物的界面，在那里它们可以调节细胞中的凝聚物功能。此前，我们设计了优先吸附在凝聚物表面的两亲性蛋白质。这些蛋白质包含一个亲凝聚物结构域（RGG）和一个疏凝聚物结构域（MBP或GST）。在此，我们通过直接定量证明，这些两亲性蛋白质起到表面活性剂的作用，以浓度依赖的方式将RGG-RGG凝聚物的界面张力从约260 μN/m降低至约100 μN/m。值得注意的是，与基于MBP的表面活性剂相比，基于GST的表面活性剂蛋白在降低界面张力方面表现出高10倍的功效。我们表明，这种功效的提高归因于其更高的表面密度，这是由GST的寡聚化能力驱动的。我们还表明，这些表面活性剂蛋白会减缓液滴融合并减小平均液滴大小，这正如典型表面活性剂所预期的那样。我们的研究结果定量地表明了表面活性剂蛋白如何通过调节界面张力在调节生物分子凝聚物的行为中发挥关键作用。
