"Engineering protein and polyion interactions for cellular applications"
Protein de-mixing has recently been implicated in the organization of cellular components. These phase separated membraneless organelles create distinct environments that are essential to cellular processes ranging from cell signaling to gene expression. Several membraneless organelles appear to have the same physical properties as complex coacervates – liquid-liquid phase separated mixtures of oppositely charged polyelectrolytes. However, protein polymers differ significantly from synthetic polyelectrolytes. Proteins are amphoteric, have low charge density, and frequently adopt a globular folded structure. These differences impact the complexation and phase separation of proteins with polyelectrolytes. We are motivated to understand protein complex coacervation in order to enable new biological applications of these materials. Toward this end, we are interested in utilizing the physical phenomenon of complex coacervation and principles underlying the formation of liquid-like biological condensates to create synthetic membraneless organelles. We have investigated the complex coacervation of engineered proteins with biological polyelectrolytes to determine predictive design rules for protein phase separation. We employ these design rules to create synthetic organelles by promoting phase separation of engineered proteins in E. coli.
