Structural analysis of a nanoparticle containing a lipid bilayer used for detergent-free extraction of membrane proteins


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.

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  1. [1]

    Lin, S. H.; Guidotti, G. Purification of membrane proteins. Methods Enzymol. 2009, 463, 619–629.

    Article  Google Scholar 

  2. [2]

    Lichtenberg, D.; Ahyayauch, H.; Alonso, A.; Goñi, F. M. Detergent solubilization of lipid bilayers: A balance of driving forces. Trends Biochem. Sci. 2013, 38, 85–93.

    Article  Google Scholar 

  3. [3]

    Bayburt, T. H.; Carlson, J. W.; Sligar, S. G. Reconstitution and imaging of a membrane protein in a nanometer-size phospholipid bilayer. J. Struct. Biol. 1998, 123, 37–44.

    Article  Google Scholar 

  4. [4]

    Borch, J.; Torta, F.; Sligar, S. G.; Roepstorff. P. Nanodiscs for immobilization of lipid bilayers and membrane receptors: Kinetic analysis of cholera toxin binding to a glycolipid receptor. Anal. Chem. 2008, 80, 6245–6252.

    Article  Google Scholar 

  5. [5]

    Bayburt, T. H.; Sligar, S. G. Membrane protein assembly into nanodiscs. FEBS Lett. 2010, 584, 1721–1727.

    Article  Google Scholar 

  6. [6]

    Denisov, I. G.; Grinkova, Y. V.; Baas, B. J.; Sligar, S. G. The ferrous-dioxygen intermediate in human cytochrome P450 3A4. Substrate dependence of formation and decay kinetics. J. Biol. Chem. 2006, 281, 23313–23318.

    Article  Google Scholar 

  7. [7]

    Leitz, A. J.; Bayburt, T. H.; Barnakov, A. N.; Springer, B. A.; Sligar, S. G. Functional reconstitution of Beta2-adrenergic receptors utilizing self-assembling nanodisc technology. BioTechniques 2006, 40, 601–612.

    Article  Google Scholar 

  8. [8]

    Shaw, A. W.; Pureza, V. S.; Sligar, S. G.; Morrissey, J. H. The local phospholipid environment modulates the activation of blood clotting. J. Biol. Chem. 2007, 282, 6556–6563.

    Article  Google Scholar 

  9. [9]

    Shaw, A. W.; McLean, M. A.; Sligar, S. G. Phospholipid phase transitions in homogeneous nanometer scale bilayer discs. FEBS lett. 2004, 556, 260–264.

    Article  Google Scholar 

  10. [10]

    Tonge, S. R.; Tighe, B. J. Responsive hydrophobically associating polymers: A review of structure and properties. Adv. Drug Deliver. Rev. 2001, 53, 109–122.

    Article  Google Scholar 

  11. [11]

    Knowles, T. J.; Finka, R.; Smith, C.; Lin, Y. P.; Dafforn, T.; Overduin, M. Membrane proteins solubilized intact in lipid containing nanoparticles bounded by styrene maleic acid copolymer. J. Am. Chem. Soc. 2009, 131, 7484–7485.

    Article  Google Scholar 

  12. [12]

    Orwick, M. C.; Judge, P. J.; Procek, J.; Lindholm, L.; Graziadei, A.; Engel, A.; Gröbner, G.; Watts, A. Detergent-free formation and physicochemical characterization of nanosized lipid-polymer complexes: Lipodisq. Angew. Chem. Int. Ed. 2012, 124, 4731–4735.

    Article  Google Scholar 

  13. [13]

    Orwick-Rydmark, M.; Lovett, J. E.; Graziadei, A.; Lindholm, L.; Hicks, M. R.; Watts, A. Detergent-free incorporation of a seven-transmembrane receptor protein into nanosized bilayer lipodisq particles for functional and biophysical studies. Nano lett. 2012, 12, 4687–4692.

    Article  Google Scholar 

  14. [14]

    Long, A. R.; O’Brien, C. C.; Malhotra, K.; Schwall, C. T.; Albert, A. D.; Watts, A.; Alder, N. N. A detergent-free strategy for the reconstitution of active enzyme complexes from native biological membranes into nanoscale discs. BMC biotechnol. 2013, 13, 41.

    Article  Google Scholar 

  15. [15]

    Bechinger, B.; Ruysschaert, J. M.; Goormaghtigh, E. Membrane helix orientation from linear dichroism of infrared attenuated total reflection spectra. Biophys. J. 1999, 76, 552–563.

    Article  Google Scholar 

  16. [16]

    Dalvit, C.; Ramage, P.; Hommel, U. Heteronuclear X-filter 1H PFG double-quantum experiments for the proton resonance assignment of a ligand bound to a protein. J. Magn. Reson. 1998, 131, 148–153.

    Article  Google Scholar 

  17. [17]

    Hwang, T. L.; Shaka, A. J. Water suppression that works. Excitation sculpting using arbitrary wave-forms and pulsed-field gradients. J. Magn. Reson. 1995, 112, 275–279.

    Article  Google Scholar 

  18. [18]

    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 

  19. [19]

    Goddard, T. D.; Kneller, D. G. SPARKY 3. University of California, San Francisco, 2004, 15.

    Google Scholar 

  20. [20]

    Kline, S. R. Reduction and analysis of SANS and USANS data using IGOR Pro. J. Appl. Cryst. 2006, 39, 895–900.

    Article  Google Scholar 

  21. [21]

    Hayter, J. B.; Penfold, J. An analytic structure factor for macroion solutions. Mol. Phys. 1981, 42, 109–118.

    Article  Google Scholar 

  22. [22]

    Smith, M. B.; McGillivray, D. J.; Genzer, J.; Lösche, M.; Kilpatrick, P. K. Neutron reflectometry of supported hybrid bilayers with inserted peptide. Soft Matter 2010, 6, 862–865.

    Article  Google Scholar 

  23. [23]

    Nagle, J. F.; Tristram-Nagle, S. Structure of lipid bilayers. BBA-Rev. Biomembranes 2000, 1469, 159–195.

    Google Scholar 

  24. [24]

    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 

  25. [25]

    Liang, C. Y.; Krimm, S. Infrared spectra of high polymers. VI. Polystyrene. J. Polym. Sci. 1958, 27, 241–254.

    Article  Google Scholar 

  26. [26]

    Raussens, V.; Narayanaswami, V.; Goormaghtigh, E.; Ryan, R. O.; Ruysschaert, J. M. Alignment of the apolipophorin-III alpha-helices in complex with dimyristoylphosphatidylcholine. A unique spatial orientation. J. Biol. Chem. 1995, 270, 12542–12547.

    Article  Google Scholar 

  27. [27]

    Fringeli, U. P.; Günthard, H. H. Infrared membrane spectroscopy. Mol. Biol. Biochem. Biophys. 1981, 31, 270–332.

    Article  Google Scholar 

  28. [28]

    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.

    Article  Google Scholar 

  29. [29]

    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 

  30. [30]

    Heimburg, T. A model for the lipid pretransition: Coupling of ripple formation with the chain-melting transition. Biophys. J. 2000, 78, 1154–1165.

    Article  Google Scholar 

  31. [31]

    Blume, A. Apparent molar heat capacities of phospholipids in aqueous dispersion. Effects of chain length and head group structure. Biochem. 1983, 22, 5436–5442.

    Article  Google Scholar 

  32. [32]

    Fejes Tóth, L. Regular Figures; Pergamon Press: Oxford, 1964; pp 339.

    Google Scholar 

  33. [33]

    Specht, E. program cci, 1999–2014.

    Google Scholar 

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Correspondence to Tim R. Dafforn.

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These authors contributed equally to the work.

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Jamshad, M., Grimard, V., Idini, I. et al. Structural analysis of a nanoparticle containing a lipid bilayer used for detergent-free extraction of membrane proteins. Nano Res. 8, 774–789 (2015).

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  • nanoparticles
  • lipid
  • polymer
  • membrane proteins
  • structure
  • detergent