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Nanodiscs – Tool for membrane protein studies

Nanodiscs are self-assembled model membranes that resemble high density lipoprotein (HDL) particles. They consist of a small lipid bilayer patch and two copies of an amphipathic membrane scaffold protein (MSP) that shield the hydrophobic rim of the membrane fragment from water. Different scaffold proteins are in use, most popular are recombinantly produced variants of human apolipoprotein A-I. Nanodiscs have been optimized, promoted, and characterized in the laboratory of Stephen G. Sligar at the University of Illinois at Urbana-Champaign.

Nanodisc1Nanodisc consisting of ~130 phospholipids and two highly helical MSP1 polypeptides.

Nanodiscs afford solubilization of membrane proteins in a functional state, thus making them available for biophysical analysis techniques previously restricted to soluble proteins.

Nanodiscs in solution NMR studies

We demonstrated that integral membrane proteins reconstituted in nanodiscs can be studied by high resolution liquid state NMR. An isotope labeled polypeptide containing the transmembrane and cytoplasmic domains of human CD4 was incorporated into nanodiscs. Two-dimensional 1H, 13C HSQC NMR spectra show correlation signals of both the 13C-labeled CD4 and the lipid molecules (13C at natural abundance).

Nanodisc31H, 13C HSQC spectrum of CD4 fragment in nanodisc. Protein (black) and lipid signals (green) are observed. Preliminary assignments are shown for selected peaks (red boxes).

Glück et al. (2009) J Am Chem Soc 131: 12060-61

Nanodiscs in surface plasmon resonance studies

Nanodisc-reconstituted integral membrane proteins can serve as analyte in SPR studies. We inserted a fusion of the transmembrane domain of CD4 and ubiquitin carrying a N-terminal decahistidine tag into nanodiscs. Binding of the nanodisc-inserted fusion protein to an immobilized antihistidine monoclonal antibody was quantified in SPR experiments.

Nanodisc4Single-cycle kinetic data reflecting the interaction of immobilized PentaHis antibody with His-Ubi-CD4 in nanodisc at two different surface activities.

Glück et al. (2010) Analytical Biochemistry 408 (1): 46-52