Stabilization of Condensate Interfaces Using Dynamic Protein Insertion.

Coacervates have been widely used to mimic membraneless organelles (MLOs). However, coacervates without a membrane or stabilizing surface do not feature the same level of stability as MLOs. This study shows that specifically engineered surface-active proteins can interact with the interface of polypeptide coacervates, conferring resistance to coacervate dissolution and fusion. Modulating the molecular characteristics of these coacervate stabilizing proteins highlighted that their dimerization aids in achieving effective interface stabilizers. Cryo-TEM imaging showed a densely packed protein monolayer at the coacervate-liquid interface, while single-molecule super-resolution microscopy captured the dynamic nature of this protein layer, with the proteins rapidly (un)docking and moving across the coacervate interface within milliseconds. These findings suggest a dynamic form of coacervate stabilization driven by transient protein interactions at the condensate interface. This unique form of coacervate stabilization not only provides a new approach to developing stable and dynamically exchanging synthetic condensate systems but, as model systems, can also significantly contribute to our understanding of the mechanisms underlying the temporal stability of MLOs in nature.