Structural Analysis of Membrane Proteins in Cell-Derived Microvesicles

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Abstract

Transmembrane signalling by membrane proteins is essential for physiological processes and disease states, making these proteins key targets for drug development. Structural biology provides unique insights into the mechanisms of membrane protein function and dysfunction caused by mutations. Most high-resolution membrane protein structures have been obtained from purified proteins using single-particle cryo-electron microscopy (cryo-EM). However, protein purification and embedding into detergent micelles or membrane mimetics can partially destabilise the proteins, limit conformational flexibility, and disrupt native protein-protein interactions present in cellular membranes. Thus, investigating membrane proteins in their natural environment is essential. Recent advancements in hardware and software for cryo-EM and cryo-electron tomography (cryo-ET) make this increasingly feasible. Here, we describe protocols for structural analysis of membrane proteins in natively derived microvesicles by cryo-ET. We focus on preparing native vesicles containing a membrane protein of interest, cryo-ET data collection, and analysis using open source software packages tomoBEAR, Dynamo, and RELION.

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ACKNOWLEDGEMENTS

We thank Dr. Thiemo Sprink and Viacheslav Kralin for valuable discussions. The authors thank the Helmholtz Society (https://www.helmholtz.de/en/) for funding. M.K. is supported by the Heisenberg Award from the DFG (KU3221/3- 1, https://www.dfg.de/). I.M.S.S is supported by the European Union’s Marie Skłodowska-Curie Fellowship, project No 101208186. The funders did not play any role in the study design, data collection, analysis, decision to publish, or manuscript preparation.

CONFLICT OF INTEREST

P.M.D. is an employee of Thermo Fisher Scientific. The other authors declare no conflicts of interest.