(686h) Tuning Supramolecular Structures Self-Assembled from Fusion Proteins Via Time- and Temperature-Controlled Coacervate Phase

Aggregation and segregation of protein-droplets in the cell has been considered as a key step in many studies to understand the origin of life. Coacervates, the spherical aggregates of protein-rich colloidal droplets driven by hydrophobic forces, can be used as a simple model for protocells which can actively grow and divide by themselves. We recently reported that designed recombinant fusion protein complexes composed of a globular domain (mCherry), leucine zipper pair (ZE/ZR) and thermo-response elastin-like polypeptide (ELP) undergo active phase transition from soluble proteins through dynamic coacervate phase to stable vesicles with increasing temperature. The coacervate phase driven by the decreased ELP solubility in water presents growth in size as a function of aging time, which dictates the self-assembled vesicle size upon further heating. Also, controlling either the pre-incubation temperature in coacervate phase or the heating rate results in different types of supramolecular assembled structures. In order to elucidate the phase transition from coacervates to higher-order assembled structures, we have traced the self-assembly properties of mCherry-zipper-ELP complexes by monitoring the changes in size, shape and concentration while varying the incubation pathways. This study gives fundamental and practical insights into understanding how the protein coacervates grow and assemble into organized structures as well as developing artificial cells with multi-compartment structures from recombinant proteins containing functional domains.