Robust nonequilibrium pathways to microcompartment assembly

Bacterial microcompartments, organelle-like, proteinaceous structures found in photosynthetic bacteria, assemble to encapsulate enzymes crucial for carbon fixation. Geometric similarities between microcompartment shells and viral capsids have inspired models of the assembly process that posit that the microcompartment represents a stable, equilibrium arrangement of its constituent proteins. This assumption does not hold, however, for shells that lack intrinsic curvature. I will discuss a microscopic model of the assembly process that is fundamentally nonequilibrium but, nevertheless, can robustly and reliably produce microcompartment structures. The essence of the dynamics of this process can be understood from a minimal mathematical model that resolves the kinetics of the protein shell and its fluctuating, internal cargo. These results highlight experimentally controllable parameters for modulating the size and shape of bacterial microcompartments in the lab.