Fig. 3

Structural characterization of Tau and K18 protein/phospholipid complexes. a NativePAGE analysis of protein/phospholipid complexes formed by Tau (left) and K18 (right) after 24 h of incubation with BPS vesicles at a molar protein:phospholipid ratio of 1:20. The monomer bands are indicated by asterisks, and the presence of higher molecular weight bands, indicated by arrows, demonstrates that the protein/phospholipid complexes contain oligomerized proteins. b Averages obtained from the classification of ~4850 particles of Tau with a radius ranging from 100 to 110 Å and ~4000 particles of K18 with a radius ranging from 81 to 97 Å into 50 classes. c CD spectra of Tau (left) and K18 (right) alone (blue) and their phospholipid complexes (red) formed by incubation with BPS vesicles at a molar protein:phospholipid ratio of 1:20. The formation of protein/phospholipid complexes is accompanied by a slight increase in secondary structure content. d Dot blots (0.25 µg) of Tau monomer or Tau incubated for 4 days with BPS vesicles at 37 °C. Tau was detected using the MC-1 antibody (dilution 1:500), which recognizes pathological Tau conformations, and a homemade rabbit polyclonal anti-Tau antibody (dilution 1:5000) to assess the total amount of protein. e Determination of the molecular weight of protein/phospholipid complexes formed by Tau and K18 by multi-angle light scattering. Although the number of subunits in the complex remains constant (5 for Tau and 7–8 for K18), the number of phospholipid decreases over time (from ~190 to ~150 for Tau and from ~160 to ~140 for K18). The final molecular weight of the protein/phospholipid complexes formed by Tau and K18 are ~335 kDa and 230 kDa, respectively. f Residue type assignments of [U-13C/15N]-labeled K18/phospholipid complexes using 2D DARR solid-state NMR spectra. Mixing times for DARR are 20 ms (blue) and 150 ms (red). Both spectra were recorded at 17.6 T, 278 K, and 13 kHz magic-angle spinning