Figure 3

NMR spectroscopy of purified MAβ:Z _Aβ3 complex. (A) ¹⁵N HSQC NMR spectrum of the ¹⁵N-labeled MAβ(1–40):Z_Aβ3 complex. The complex was obtained from coexpression and purified by IMAC (elution of the intact complex with 150 mM imidazole) and SEC. (B)-(D) Comparison of the glycine region (B; boxed area in panel A) with corresponding regions of ¹⁵N HSQC spectra of Aβ(1–40):Z_Aβ3 samples in which either Z_Aβ3 (C) or Aβ(1–40) (D) are ¹⁵N-labeled. Sequential assignments of glycine resonances for the two Z_Aβ3 subunits and bound Aβ(1–40) are given in panels C and D, respectively. The occurrence of resonances at identical chemical shifts in complexes of Z_Aβ3 with recombinant MAβ(1–40) and native Aβ(1–40) peptides indicates that the structures of the two complexes are the same. NMR was measured at 25°C at 800 MHz (A, B and D) or 900 MHz (C) on samples containing 160 μM (A, B), 450 μM (C) or 400 μM (D) complex in 20 mM potassium (A, B) or sodium (C, D) phosphate, with 0.1% azide and 10% D₂O at pH 7.2.