Fig. 2.
Intermediates on the misfolding pathway of PrP dimers. (A) WLC fits (dashed lines) to representative type 1 (black) and 2 (blue) FECs reveal contour length changes (∆Lc) in the dimer. The total ∆Lc (gray lines) is 56 nm for type 2 and 81 nm for type 1, compared with 34 nm for a single PrPC domain. For both FEC types, an intermediate, ID1 (red), unfolds at ∼13 pN; a “shoulder” with non-WLC behavior at 5–10 pN indicates additional intermediates. (B) The shoulder feature in type 1 FECs was best fit assuming one additional transition (red) corresponding to ID2–ID1 transitions in type 2 FECs, rather than none (yellow), as shown by the residuals (Inset). (C) An average (black) of type 2 FECs (gray) was best fit in the shoulder region by a model assuming two additional transitions in sequence (red) rather than only one (yellow), as shown by the fit residuals (Inset). Unfolding occurred sequentially via three intermediates: ID3, ID2, and ID1.