Co-translational association of cell-free expressed membrane proteins with supplied lipid bilayers

Abstract

Routine strategies for the cell-free production of membrane proteins in the presence of detergent micelles and for their efficient co-translational solubilization have been developed. Alternatively, the expression in the presence of rationally designed lipid bilayers becomes interesting in particular for biochemical studies. The synthesized membrane proteins would be directed into a more native-like environment and cell-free expression of transporters, channels or other membrane proteins in the presence of supplied artificial membranes could allow their subsequent functional analysis without any exposure to detergents. In addition, lipid-dependent effects on activity and stability of membrane proteins could systematically be studied. However, in contrast to the generally efficient detergent solubilization, the successful stabilization of membrane proteins with artificial membranes appears to be more difficult. A number of strategies have therefore been explored in order to optimize the co-translational association of membrane proteins with different forms of supplied lipid bilayers including liposomes, bicelles, microsomes or nanodiscs. In this review, we have compiled the current state-of-the-art of this technology and we summarize parameters which have been indicated as important for the co-translational association of cell-free synthesized membrane proteins with supplied membranes.

Keywords::

• Lipid bilayer
• liposome
• reconstitution

Acknowledgements

This work was supported by the Collaborative Research Center (SFB) 807 of the German Research Foundation (DFG). We further thank the European Drug Initiative on Channels and Transporters (EDICT), contract number HEALTH-F4-2007-201924, the European initiative on Structural Biology of Membrane Proteins (SBMP), contract number PITN-GA-2008-211800 and the NIH (grant number U54 GM094608) for funding.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.