Formation of Biomolecular Condensates in Bacteria by Tuning Protein Electrostatics

While eukaryotic cells have a myriad
of membrane-bound organelles enabling the isolation of different chemical
environments, prokaryotic cells lack these defined reaction vessels.
Biomolecular condensatesorganelles that lack a membraneprovide
a strategy for cellular organization without a physical barrier while
allowing for the dynamic, responsive organization of the cell. It
is well established that intrinsically disordered protein domains
drive condensate formation via liquid–liquid phase separation;
however, the role of globular protein domains on intracellular phase
separation remains poorly understood. We hypothesized that the overall
charge of globular proteins would dictate the formation and concentration
of condensates and systematically probed this hypothesis with supercharged
proteins and nucleic acids in E. coli. Within this
study, we demonstrated that condensates form via electrostatic interactions
between engineered proteins and RNA and that these condensates are
dynamic and only enrich specific nucleic acid and protein components.
Herein, we propose a simple model for the phase separation based on
protein charge that can be used to predict intracellular condensate
formation. With these guidelines, we have paved the way to designer
functional synthetic membraneless organelles with tunable control
over globular protein function.