Figure 1. NMR Assays Suggest that Nanodiscs Associate with Opposite Sides of the HPX Domain of MT1-MMP.

(A) Bilayer proximities of Ile/Leu/Val side chains were measured to DMPC nanodiscs encircled by MSP1D1 (Denisov et al., 2004) doped with an average of two nitroxide spin-labeled PC molecules per leaflet. The resulting PREs were plotted as Γ₂ = R_{2, paramag} – R_2,diamag, the difference between methyl proton relaxation rates with and without doxyl-substituted PC. Γ₂ values resulting from addition of 10-doxyl PC or 5-doxyl PC are plotted in pink triangles and green spheres, respectively. The symbols are filled where Γ₂ > 30/s. The uncertainties indicated are those of the fits of the exponential decays and their differences.

(B) Ile/Leu/Val side chains with Γ₂ > 30/s are marked on the crystal structure of the HPX domain (PDB: 3C7X) with spheres which are pink if near 10-doxyl PC and green if near 5-doxyl PC only. The blades of the β-propeller are colored blue for I, green for II, yellow for III, and pink IV, respectively, and throughout this article.

(C) Addition of the nanodiscs to the HPX domain in a 1:1 molar ratio induced the radial chemical shift perturbations (CSPs), quantified using eq. 2. CSPs exceeding 0.03 ppm are highlighted in orange.

(D) Sites of the larger CSPs (Δω_HN > 0.03 ppm) are plotted as spheres on the backbone.

See also Fig. S1.