Influence of Assay Parameters on Structural and Functional Studies of Membrane Proteins

Abstract

Structural and functional characterization of membrane proteins (MPs) requires extraction from the native lipid bilayer, which generally necessitates the formation of water-soluble MPs structures or complexes suitable for biochemical assays. These structures are often detergent micelles that form protein-detergent complexes (PDCs), due to detergents being straightforward
in implementation and providing homogenous yields. However, obtaining physiologically relevant PDCs remains a challenge, because most detergents do not keep the native structure/function of the protein intact, jeopardizing its stability, and disrupting the proton pressure and electric gradient even after reincorporation in artificial lipid membranes. To achieve native-like
physiology (i.e. to maintain native protein-associated lipids and structurally relevant ligands or cofactors), it is essential to choose the right extraction parameters. Nevertheless, the field of membrane biochemistry is still missing a holistic, interdependent understanding of these systems, too often neglecting the evident, key role that detergents play. In this review, we aim to obtain a more fundamental understanding of detergent-solubilized membrane proteins by pinpointing the most relevant assay parameters (i.e. the most influential on the biochemical properties) involving MPs.