Autoinsertion (LAiR): rapid functional reconstitution of integral membrane proteins into lipid bilayers

Abstract

Functional investigation of purified integral membrane proteins (IMPs) is hampered by the need to insert these hydrophobic proteins from the detergent-solubilized state into liposomal membranes. Here we report reintegration of IMPs into a lipid environment within minutes, an order of magnitude faster than currently used standard techniques. The new approach yielded optimal results for IMPs solubilized in the detergent lauryl-maltose neopentyl glycol (LMNG) and is therefore termed LMNG Auto-insertion Reintegration (LAiR). LAiR displays superior performance to standard methods in terms of protein activity, long-term stability and proton tightness of proteoliposomes. LAiR reconstituted vectorial control of membrane-bound activity by the transmembrane ion motive force, a property particularly important in mitochondrial function, which was undetectable by standard reintegration methods. LAiR also preserved fragile IMP properties that are prone to disruption upon reintegration, including long-term multi-subunit integrity, inhibitor susceptibility, and higher-order oligomeric states. LAiR proved suitable for reintegration into liposomes as well as into surface-tethered membrane bilayers, and was compatible with IMPs and lipids from prokaryotic and eukaryotic sources. We anticipate a broad scope for LAiR as a powerful tool in fundamental research, pharmaceutical applications, and biotechnology.