Structural Analysis of Membrane Proteins in Cell-Derived Microvesicles.

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.