Modeling the Coacervation of Artificial Membraneless Organelles in Synthetic Cells
Organelles serve to compartmentalize cells and allow for highly regulated and specialized functioning. While most Eukaryotic organelles are contained using lipid bilayers, it has been discovered that some organisms also contain organelles that lack a lipid membrane. Instead, these organelles rely on the phenomenon of liquid-liquid phase separation of so-called intrinsically disordered proteins (IDPs) to form droplet-like structures called coacervates. These structures are highly versatile, as they can form and dissociate depending on environmental conditions such as temperature, protein concentration, and/or salt concentration. Upon their formation or dissociation, they can sequester or release other macromolecules in the cell to control gene expression. In this project, a type of IDP called an Elastin-Like Polypeptide (ELP) is used as a simple model of a membraneless organelle. This protein is expressed in vitro, and the critical concentration (the concentration at which it will begin to form coacervates) is determined. It is also shown that upon encapsulation in a liposomal vesicle (synthetic cell), the critical concentration of the protein is further altered. Future work will involve expressing this ELP inside of liposomes using an in vitro protein expression system, and demonstrating the temperature-induced coacervation of the protein within these vesicles. Following this, we hope to functionalize these coacervates to allow them to sequester and release specific RNA payloads to control gene expression.