We are studying a novel method using the styrene–maleic copolymer to directly extract membrane proteins from cellular membranes in the form of native nanodiscs (Dörr et al., Eur. Biophys. J., 2016, 45:3–21). Membrane proteins isolated in this manner are generally very stable and, unlike in conventional detergent-based extractions, their native complexes with both other proteins and lipids are conserved. Our project aims at isolating the human peptide-loading complex that is essential for antigen presentation in native nanodiscs and at structurally characterizing the obtained particles using cryo-electron microscopy methods to elucidate complex organization.