Journal: Proc Natl Acad Sci U S A / Year: 2020 Title: Cryo-EM analysis of a membrane protein embedded in the liposome. Authors: Xia Yao / Xiao Fan / Nieng Yan / Abstract: Membrane proteins (MPs) used to be the most difficult targets for structural biology when X-ray crystallography was the mainstream approach. With the resolution revolution of single-particle electron ...Membrane proteins (MPs) used to be the most difficult targets for structural biology when X-ray crystallography was the mainstream approach. With the resolution revolution of single-particle electron cryo-microscopy (cryo-EM), rapid progress has been made for structural elucidation of isolated MPs. The next challenge is to preserve the electrochemical gradients and membrane curvature for a comprehensive structural elucidation of MPs that rely on these chemical and physical properties for their biological functions. Toward this goal, here we present a convenient workflow for cryo-EM structural analysis of MPs embedded in liposomes, using the well-characterized AcrB as a prototype. Combining optimized proteoliposome isolation, cryo-sample preparation on graphene grids, and an efficient particle selection strategy, the three-dimensional (3D) reconstruction of AcrB embedded in liposomes was obtained at 3.9 Å resolution. The conformation of the homotrimeric AcrB remains the same when the surrounding membranes display different curvatures. Our approach, which can be widely applied to cryo-EM analysis of MPs with distinctive soluble domains, lays out the foundation for cryo-EM analysis of integral or peripheral MPs whose functions are affected by transmembrane electrochemical gradients or/and membrane curvatures.
History
Deposition
May 25, 2020
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Header (metadata) release
Jul 15, 2020
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Map release
Jul 15, 2020
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Update
Aug 19, 2020
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Current status
Aug 19, 2020
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
EMPIAR-10426 (Title: 3.9 Angstrom reconstruction of E.coli AcrB embedded in the liposome Data size: 9.6 TB Data #1: Unaligned multi-frame micrographs of AcrB embedded in the liposome. [micrographs - multiframe])
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