Nanoscopic Dynamics Dictate the Phase Separation Behavior of Intrinsically Disordered Proteins

摘要

Many intrinsically disordered proteins (IDPs) in nature may undergo liquid–liquid phase separation to assemble membraneless organelles with varied liquid-like properties and stability/dynamics. While solubility changes underlie these properties, little is known about hydration dynamics in phase-separating IDPs. Here, by studying IDP polymers of similar composition but distinct liquid-like dynamics and stability upon separation, namely, thermal hysteresis, we probe at a nanoscopic level hydration/dehydration dynamics in IDPs as they reversibly switch between phase separation states. Using continuous-wave electron paramagnetic resonance (CW EPR) spectroscopy, we observe distinct backbone and amino acid side-chain hydration dynamics in these IDPs. This nanoscopic view reveals that side-chain rehydration creates a dynamic water shield around the main-chain backbone that effectively and counterintuitively prevents water penetration and governs IDP solubility. We find that the strength of this superficial water shell is a sequence feature of IDPs that encodes for the stability of their phase-separated assemblies. Our findings expose and offer an initial understanding of how the complexity of nanoscopic water–IDP interactions dictate their rich phase separation behavior.