Structural analysis of a nanoparticle containing a lipid bilayer used for detergent-free extraction of membrane proteins
- 1.4k Downloads
In the past few years there has been a growth in the use of nanoparticles for stabilizing lipid membranes that contain embedded proteins. These bionanoparticles provide a solution to the challenging problem of membrane protein isolation by maintaining a lipid bilayer essential to protein integrity and activity. We have previously described the use of an amphipathic polymer (poly(styrene-co-maleic acid), SMA) to produce discoidal nanoparticles with a lipid bilayer core containing the embedded protein. However the structure of the nanoparticle itself has not yet been determined. This leaves a major gap in understanding how the SMA stabilizes the encapsulated bilayer and how the bilayer relates physically and structurally to an unencapsulated lipid bilayer. In this paper we address this issue by describing the structure of the SMA lipid particle (SMALP) using data from small angle neutron scattering (SANS), electron microscopy (EM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC) and nuclear magnetic resonance spectroscopy (NMR). We show that the particle is disc shaped containing a polymer “bracelet” encircling the lipid bilayer. The structure and orientation of the individual components within the bilayer and polymer are determined showing that styrene moieties within SMA intercalate between the lipid acyl chains. The dimensions of the encapsulated bilayer are also determined and match those measured for a natural membrane. Taken together, the description of the structure of the SMALP forms the foundation for future development and applications of SMALPs in membrane protein production and analysis.
Keywordsnanoparticles lipid polymer membrane proteins structure detergent
Unable to display preview. Download preview PDF.
- Delaglio, F.; Grzesiek, S.; Vuister, G. W.; Zhu, G.; Pfeifer, J.; Bax, A. NMRPipe: A multidimensional spectral processing system based on UNIX pipes. J. Bio. NMR 1995, 6, 277–293.Google Scholar
- Goddard, T. D.; Kneller, D. G. SPARKY 3. University of California, San Francisco, 2004, 15.Google Scholar
- Nagle, J. F.; Tristram-Nagle, S. Structure of lipid bilayers. BBA-Rev. Biomembranes 2000, 1469, 159–195.Google Scholar
- Goormaghtigh, E.; Raussens, V.; Ruysschaert, J. M. Attenuated total reflection infrared spectroscopy of proteins and lipids in biological membranes. BBA-Rev. Biomembranes 1999, 1422, 105–185.Google Scholar
- Lewis, R. N.; Pohle, W.; McElhaney, R. N. The interfacial structure of phospholipid bilayers: Differential scanning calorimetry and Fourier transform infrared spectroscopic studies of 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine and its dialkyl and acyl-alkyl analogs. Biophys. J. 1996, 70, 2736–2746.CrossRefGoogle Scholar
- Wald, J. H.; Coormaghtigh, E.; Meutter, J. D.; Tuysschaert, J. M.; Jonas, A. Investigation of the lipid domains and apolipoprotein orientation in reconstituted high density lipoproteins by fluorescence and IR methods. J. Biol. Chem. 1990, 265, 20044–20050.Google Scholar
- Fejes Tóth, L. Regular Figures; Pergamon Press: Oxford, 1964; pp 339.Google Scholar
- Specht, E. program cci, 1999–2014.Google Scholar