Mass Photometry of Membrane Proteins

Integral membrane proteins (IMPs) are biologically highly significant but challenging to study because they require maintaining a cellular lipid-like environment. Here, we explore the application of mass photometry (MP) to IMPs and membrane-mimetic systems at the single-particle level. We apply MP to amphipathic vehicles, such as detergents and amphipols, as well as to lipid and native nanodiscs, characterizing the particle size, sample purity, and heterogeneity. Using methods established for cryogenic electron microscopy, we eliminate detergent background, enabling high-resolution studies of membrane-protein structure and interactions. We find evidence that, when extracted from native membranes using native styrenemaleic acid nanodiscs, the potassium channel KcsA is present as a dimer of tetramers-in contrast to results obtained using detergent purification. Finally, using lipid nanodiscs, we show that MP can help distinguish between functional and non-functional nanodisc assemblies, as well as determine the critical factors for lipid nanodisc formation.

Automated summary

This study explores the application of mass photometry (MP) to Integral membrane proteins (IMPs) and membrane-mimetic systems at the single-particle level. By applying MP to amphipathic vehicles and lipid nanodiscs, the research characterizes particle size, sample purity, and heterogeneity, enabling high-resolution studies of membrane-protein structure and interactions. Evidence suggests that using native styrenemaleic acid nanodiscs could reveal new insights into the structure of membrane proteins compared to conventional detergent purification methods.