Polymer-Mediated Synthesis and Incorporation of Membrane Protein in Phospholipid Vesicles

Membrane proteins play significant roles in cellular activities, and remain attractive pharmacological targets. Studying membrane protein folding out of biological environments remains an intriguing endeavor for both biophysical and biological communities. Small molecular detergents are generally used to solubilize membrane proteins during in vitro characterization, which usually perturb protein structures and functions. Here, we show a synthetic polymer system that mimics protein folding chaperones by tailoring polymer amphiphilicity and charges. Specifically, a series of polymers have been developed that enable direct cell-free synthesis of a channel protein, PepTso (peptide transporter) and a water channel protein Aquaporin Z, which fold properly in aqueous environment. Protein synthesis in the presence of both liposomes and the polymers result in the incorporation of proteins into phospholipid bilayers, and allow proteins to transport oligopeptides and waters across liposome membrane respectively. Notably, the results validate our hypothesis that the polymer can serve as a synthetic chaperone that sequesters the membrane proteins from water and still retains their structures and functionalities.