Fig. 3.
Molecular description of the IT state using X-ray crystallography and high resolution solution NMR. (A) The ribbon overlay shows one monomer of the hexameric crystal structure of H13F (PDB code 3CIQ [55], in blue) and the lowest energy structure of ΔN6 (PDB code 2XKU) [9] (in red). The residues Phe30, Pro32, Trp60, Phe62 and His84 are highlighted in sticks. The dashed green box indicates a zoom-in for this region shown in (B). (C) 1H–15N HSQC of wild-type β2m in 18% (v/v) TFE at pH 6.6 and 33 °C (reproduced, with permission, from [20]). Green circles are assigned resonances for IT, while blue circles indicate the TFE induced, structurally disordered D state that is thought to be precursor for fibril elongation under these conditions. (D) 1H–15N HSQC overlay of wild-type β2m (black) and ΔN6 (red) recorded in 25 mm sodium phosphate buffer pH 7.5, 25 °C. (E) 1H–15N SOFAST HMQC overlay of ΔN6 (red) and the kinetic intermediate IT (green) recorded approximately 2 min after refolding was initiated (25 mm sodium phosphate buffer pH 7.5, 0.8 m residual urea, 25 °C). Reproduced with permission from [9].