Synthesis and Evaluation of a Library of Alternating Amphipathic Copolymers to Solubilize and Study Membrane Proteins

Amphipathic copolymers such as poly(styrene-maleic acid) (SMA) are promising tools for the facile extraction of membrane proteins (MPs) into native nanodiscs. Here, we designed and synthesized a library of well-defined alternating copolymers of SMA analogues in order to elucidate polymer properties that are important for MP solubilization and stability. MP extraction efficiency was determined using KcsA from E. coli membranes, and general solubilization efficiency was investigated via turbidimetry experiments on membranes of E. coli, yeast mitochondria, and synthetic lipids. Remarkably, halogenation of SMA copolymers dramatically improved solubilization efficiency in all systems, while substituents on the copolymer backbone improved resistance to Ca2+. Relevant polymer properties were found to include hydrophobic balance, size and positioning of substituents, and electronic effects. The thus contributes to the rational of for the of MPs.

Automated summary

In this study, a library of well-defined alternating copolymers of SMA analogues was designed and synthesized, revealing important polymer properties for membrane protein solubilization and stability. Remarkably, halogenation of the SMA copolymers significantly improved solubilization efficiency, while substituents on the copolymer backbone enhanced resistance to Ca2+.