Kota Divya, Prasad Ramesh, Zhou Huan-Xiang
Department of Chemistry, University of Illinois Chicago, Chicago IL 60607, USA.
Department of Physics, University of Illinois Chicago, Chicago IL 60607, USA.
bioRxiv. 2023 Aug 20:2023.08.20.554035. doi: 10.1101/2023.08.20.554035.
ATP is an abundant molecule with crucial cellular roles as the energy currency and a building block of nucleic acids and for protein phosphorylation. Here we show that ATP mediates the phase separation of basic intrinsically disordered proteins (bIDPs). In the resulting condensates, ATP is highly concentrated (apparent partition coefficients at 200-5000) and serves as bridges between bIDP chains. These liquid-like droplets have some of the lowest interfacial tension (25 pN/μm) but high zero-shear viscosities (1-15 Pa s) due to the bridged protein networks, and yet their fusion has some of the highest speeds (1 μm/ms). The rapid fusion manifests extreme shear thinning, where the apparent viscosity is lower than zero-shear viscosity by over 100-fold, made possible by fast reformation of the ATP bridges. At still higher concentrations, ATP does not dissolve bIDP droplets but results in aggregates and fibrils.
ATP是一种丰富的分子，在细胞中具有关键作用，作为能量货币、核酸的组成成分以及用于蛋白质磷酸化。在这里，我们表明ATP介导了碱性内在无序蛋白（bIDP）的相分离。在形成的凝聚物中，ATP高度浓缩（表观分配系数为200 - 5000），并作为bIDP链之间的桥梁。这些类似液体的液滴具有一些最低的界面张力（约25 pN/μm），但由于桥接的蛋白质网络而具有高零剪切粘度（1 - 15 Pa·s），然而它们的融合具有一些最高的速度（约1 μm/ms）。快速融合表现出极端的剪切变稀，其中表观粘度比零剪切粘度低100倍以上，这是由ATP桥的快速重新形成实现的。在更高浓度下，ATP不会溶解bIDP液滴，而是导致聚集体和纤维形成。
