Engineering Synthetic Organelles to Spatially Organize Biochemical Reactions in Artificial Cells and Cell-Free Systems

Living cells have evolved numerous mechanisms to spatially organize reactions in their interior. In fact, compartmentalization is a defining characteristic of eukaryotic cells with their membrane-bound and membraneless organelles. By colocalizing specific reactions and separating others, synthetic organelles have the potential to improve the biochemical capabilities of artificial cells and cell-free systems. Simplified and engineerable models of natural cellular organelles will also lead to a better fundamental understanding of the effects of spatial organization on biochemical reactions. We have recently reported porous polymer cell-mimics with artificial nucleus-like compartments. Artificial nuclei composed of a clay-DNA hydrogel contain the templates for transcription and translation, which program cell-mimics to communicate with their neighbors. In addition, we are currently developing an artificial organelle system that consists of liquid, phase-separated lipid sponge droplets formed by a synthetic glycolipid. Droplets can sequester both hydrophobic and hydrophilic molecules, and in contrast to membrane-bound vesicles, encapsulated cargo remains in contact with the surrounding medium. Highly-efficient sequestration of specific proteins into droplets can be programmed by affinity tags, and we use this property to study the effects of colocalization and separation on enzymatic reactions. For instance, light-responsive release and encapsulation of proteins allows us to dynamically control ClpXP-mediated protein degradation by switching between proteolysis and protection of the substrate. Our results suggest that artificial organelle structures built from synthetic materials facilitate the engineering of spatial organization and will help integrate increasingly complex functions in artificial cells and cell-free systems.