Proteome Analysis of Phase-Separated Condensed Proteins with Ionic Surfactants Revealed Versatile Formation of Artificial Biomolecular Condensates

The
formation of highly condensed, native proteins is important
for the development of protein-based drugs and materials. In the cell,
various types of liquid droplets with broad functions are formed by
the spontaneous condensation of protein, as a physiological response.
These droplets lack a surrounding membrane but are phase-separated
from the water medium. These types of phase-separated states of proteins
have potential applications in biotechnology. Recently, we have developed
an artificial phase-separated liquid of condensed native proteins,
termed a protein condensate (PC), formed by electrostatic complexation
with ionic surfactants. Here we report the applicability of PC formation,
studied using an E. coli extract as the protein source.
The addition of anionic and cationic surfactants at a specific ratio
to the E. coli extract resulted in PC formation.
A proteome analysis showed that the PC thus formed contained about
600 kinds of proteins, representing 65% of the uniquely detected proteins
and confirming the high versatility of PC formation. A statistical
analysis revealed that a variety of types of proteins with a wide
range of molecular weights and isoelectric points could form PCs.