Drop Dilution Enables the Use of PEG-Derived Detergents for Membrane Protein Purification

Abstract

PEG detergents are important tools in the biophysical characterization of membrane protein whose utility is often limited by their intrinsic denaturing properties. This work addresses the question of whether changing the linker between PEG headgroup and nonpolar tail can modulate the denaturing properties of these detergents. To address this question, herein, we introduce the modular architecture of PEG550 detergents and explore its utility for protein purification from membranes and detergent exchange. Our results indicate that PEG550 detergents cannot efficiently solubilize proteins from lysed bacterial membranes. Varying the linker cannot eliminate the denaturing properties that PEG550 detergents can have on a protein during extraction and affinity purification. Interestingly, we find that PEG550 detergents can preserve the secondary structure and activity of the model membrane protein vitamin B12 transporter as good as the reference detergent n-dodecyl-β-D-maltoside following detergent exchange via drop dilution. Our findings clarify that denaturing properties of PEG550 detergents depend on both their chemical structure and the detergent exchange method with which proteins and detergents are brought together. Our drop dilution conditions are representative of those frequently employed in the biophysical characterization of membrane proteins. We anticipate PEG550 detergents will deliver a starting point for the optimization of sample properties in the biophysical characterization of membrane proteins.