Invention:
This invention is an automated label-free method to measure the affinity of membrane proteins for lipids by using conventional small molecule mass spectrometry (MS) to monitor lipid exchange between lipoprotein nanoparticles called nanodiscs. We call this method lipid exchange-mass spectrometry (LX-MS). The concept is that if a membrane protein binds a certain type of lipid, it will shift the equilibrium distribution of lipids between empty (tagged) nanodiscs and membrane protein (untagged) nanodiscs. We quantify the equilibrium distribution by measuring the lipid composition in the membrane protein nanodiscs after exchange. By titrating the lipid composition, we can determine the optimal ratio of lipids surrounding a membrane protein. This assay should be general to any membrane proteins or lipids and uses small amounts of samples.
Background:
Membrane proteins make up the majority of drug targets yet only account for 2–3% of high-resolution structures. Thus, there is a great need for improvements in structural biology and drug discovery with membrane proteins. One important question is how membrane proteins interact with lipids and remodel their local lipid environment. It is clear that the lipid environment can be critical for membrane protein structure and function, but there are no methods to measure the optimal lipid composition for membrane proteins. Current methods of screening different lipid compositions are inefficient and costly.
Applications:
- Drug discovery
- Structural biology research
Advantages:
- Quantitative design for lipid-membrane systems
- Label-free
- Design for automation
