Cycloalkane-modified amphiphilic polymers provide direct extraction of membrane proteins for CryoEM analysis
A.J. Higgins, Alex J. Flynn, Anaïs Marconnet, Laura J. Musgrove, Vincent L. G. Postis, Jonathan D. Lippiat, Chun‐wa Chung, Tom Ceska, Manuela Zoonens, Frank Sobott, Stephen P. Muench
Abstract
Abstract Membrane proteins are essential for cellular growth, signalling and homeostasis, making up a large proportion of therapeutic targets. However, the necessity for a solubilising agent to extract them from the membrane creates challenges in their structural and functional study. Although amphipols have been very effective for single-particle electron cryo-microscopy (cryoEM) and mass spectrometry, they rely on initial detergent extraction before exchange into the amphipol environment. Therefore, circumventing this pre-requirement would be a big advantage. Here we use an alternative type of amphipol: a cycloalkane-modified amphiphile polymer (CyclAPol) to extract Escherichia coli AcrB directly from the membrane and demonstrate that the protein can be isolated in a one-step purification with the resultant cryoEM structure achieving 3.2 Å resolution. Together this work shows that cycloalkane amphipols provide a powerful approach for the study of membrane proteins, allowing native extraction and high-resolution structure determination by cryoEM.