Extraction and reconstitution of membrane proteins into lipid nanodiscs encased by zwitterionic styrene-maleic amide copolymers

Mariana C Fiori,Guillermo A Altenberg,Wan Zheng,Hongjun Liang,Geuel Simiyu,Elizabeth Kamilar

doi:10.1038/s41598-020-66852-7

Mariana C Fiori, Guillermo A Altenberg + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-66852-7

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Abstract

Membrane proteins can be reconstituted in polymer-encased nanodiscs for studies under near-physiological conditions and in the absence of detergents, but traditional styrene-maleic acid copolymers used for this purpose suffer severely from buffer incompatibilities. We have recently introduced zwitterionic styrene-maleic amide copolymers (zSMAs) to overcome this limitation. Here, we compared the extraction and reconstitution of membrane proteins into lipid nanodiscs by a series of zSMAs with different styrene:maleic amide molar ratios, chain sizes, and molecular weight distributions. These copolymers solubilize, stabilize, and support membrane proteins in nanodiscs with different efficiencies depending on both the structure of the copolymers and the membrane proteins.

Highlights

Membrane proteins can be reconstituted in polymer-encased nanodiscs for studies under nearphysiological conditions and in the absence of detergents, but traditional styrene-maleic acid copolymers used for this purpose suffer severely from buffer incompatibilities
Two features of SMAs make them highly desirable: 1) SMALPs can be produced by direct membrane solubilization with SMA copolymers, maintaining the membrane proteins in a lipid bilayer and avoiding the use of detergents[14,15,16], and 2) SMALPs can be formed from proteoliposomes of known lipid composition, which is useful to study the role of membrane lipids in determining membrane protein structure and function[14,15,16]
We focused on 1:1 styrene:maleic amide molar ratio (St:MA) zwitterionic styrene-maleic amide copolymers (zSMAs) with molecular weight greater than 10 kDa19

Summary

Introduction

Membrane proteins can be reconstituted in polymer-encased nanodiscs for studies under nearphysiological conditions and in the absence of detergents, but traditional styrene-maleic acid copolymers used for this purpose suffer severely from buffer incompatibilities. We compared the extraction and reconstitution of membrane proteins into lipid nanodiscs by a series of zSMAs with different styrene:maleic amide molar ratios, chain sizes, and molecular weight distributions. These copolymers solubilize, stabilize, and support membrane proteins in nanodiscs with different efficiencies depending on both the structure of the copolymers and the membrane proteins. The main reasons for this are the broad use of SMA and SMALP, and the fact that “MA” can be still used to represent the new maleic amide moieties We showed that these new copolymers are able to solubilize membrane proteins into nanodiscs of controlled sizes[19]. Our results show that the zSMAs solubilize, stabilize, and support membrane proteins in nanodiscs with different efficiency depending on both the structure of the copolymers and the type of the membrane proteins

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Conclusion