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, characterising 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 styrene - maleic 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.

Order-disorder transitions of cytoplasmic N-termini in the mechanisms of P-type ATPases

Membrane protein structure and function are modulated via interactions with their lipid environment. This is particularly true for the integral membrane pumps, the P-type ATPases. These ATPases play vital roles...

Cryo-temperature effects on membrane protein structure and dynamics

Cryo-electron structures revolutionize biology, yet cooling effects are unclear. Using a simulation protocol of hot, cold, and rapidly cooled γ-secretase we identify cryo-contraction and modes relevant to Aβ production and cryo-analysis in general.