Abstract
The study of membrane proteins remains challenging, especially in a native membrane environment. Recently, major progress has been made using maleic acid copolymers, such as styrene maleic acid, to purify membrane proteins and study them directly with native lipids associated with the membrane. Additional maleic acid copolymers, such as diisobutylene maleic acid (DIBMA) membrane-mimetic systems, are being developed and found to have improved spectroscopic properties and pH stability. We studied DIBMA and its lipid particles in solution to better understand its assembly, without and with the lipids, to provide an insight regarding how to use it in solution for better membrane extraction. Using small-angle neutron and X-ray scattering (SANS/SAXS), we show that DIBMA organizes into structures of different size scales at various concentrations and ionic strengths. The polymer performed reasonably well under most solvent conditions except in very low concentrations and high-salt conditions that could result in limited interaction with lipids. To explore DIBMA lipid particles as a suitable membrane-mimetic system for neutron scattering studies of membrane proteins, we measured and determined the contrast-matching point of DIBMA to be ∼12% (v/v) D2O - similar to that of most protiated lipid molecules but distinct from that of regular protiated proteins - providing a natural contrast for separating their neutron scattering signals. Using SANS contrast variation, we demonstrated that the scattering from the whole lipid particle can be annihilated. Further, we determined that a well-defined lipid nanodisc structure with DIBMA was contrast-matched. These results demonstrate that the DIBMA lipid particle is an outstanding "stealth"membrane-mimetic for membrane proteins. The results provide a structural framework for understanding the organization and assembly process of the polymer itself and the lipid molecules. Such an understanding is imperative for structural techniques such as cryo-electron microscopy, nuclear magnetic resonance, small-angle scattering, and other biophysical techniques.
| Original language | English |
|---|---|
| Pages (from-to) | 4760-4768 |
| Number of pages | 9 |
| Journal | ACS Applied Bio Materials |
| Volume | 4 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jun 21 2021 |
Bibliographical note
Publisher Copyright:© 2021 American Chemical Society.
Funding
This research was supported in part by an appointment to the ORNL Oak Ridge Science Semester Program sponsored by the US Department of Energy (DOE) and was administered by the Oak Ridge Institute for Science and Education. This research used resources at the HFIR and SNS, DOE Office of Science User Facilities operated by ORNL. The Bio-SANS of the Center for Structural Molecular Biology at HFIR is supported by the DOE Office of Biological and Environmental Research. This research used resources of the Advanced Photon Source (APS), a DOE Office of Science User Facility-operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. The DO used in this research was supplied by DOE’s Isotope Program in the Office of Nuclear Physics. We thank Dr. Xiaobing Zuo for SAXS experiments at APS. We thank Qiu Zhang for assistance on sample preparation. We thank Dr. Volker Urban for discussion. 2
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Office of Science | |
| Biological and Environmental Research | |
| Argonne National Laboratory | DE-AC02-06CH11357 |
| Oak Ridge Institute for Science and Education |
Keywords
- DIBMA
- SANS
- lipid nanodisc
- lipid particle
- membrane protein
- membrane-mimetic
- neutron scattering
- small-angle scattering