Cycloalkane-modified amphiphilic polymers provide direct extraction of membrane proteins for CryoEM analysis

Commun Biol. 2021 Nov 25;4(1):1337. doi: 10.1038/s42003-021-02834-3.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cryoelectron Microscopy / instrumentation
  • Cryoelectron Microscopy / methods*
  • Cycloparaffins / chemistry*
  • Escherichia coli / physiology*
  • Escherichia coli Proteins / isolation & purification*
  • Multidrug Resistance-Associated Proteins / isolation & purification*
  • Polymers / chemistry*


  • AcrB protein, E coli
  • Cycloparaffins
  • Escherichia coli Proteins
  • Multidrug Resistance-Associated Proteins
  • Polymers