A Background Enzymatic Active Bath Affects Liquid-Liquid Phase Separation (LLPS) of Proteins

The cell interior is an active bath driven by a myriad of enzymes. It is an open problem as to how this background activity can affect physical processes in the cell, including liquid-liquid phase separation. We seek to experimentally reconstitute a model system for an active bath of enzymes to determine the effects on the liquid phase separation of a model condensate protein. We will use urease, an exothermic and kinetically fast enzyme that converts urea to carbon dioxide and ammonia, as the background enzyme. The protein that phase separates at high enough salt concentration is ubiquilin-2(UBQLN2). With the newly developed microfluidic chamber that flushes out carbon dioxide and ammonia while maintaining the concentration of urea, we showed that an active bath can prompt protein condensation. In addition, to provide some theoretical interpretation for our experimental results, we implement polymer-based molecular dynamics simulations via a sticker-spacer polymer model that can recapitulate protein condensation in the presence of active particles.