Figure 4
Force-extension curves with sawtooth patterns and characteristic of specific conformational changes observed for CNTN4 in smFS AFM. (a) Force-extension curves with similar unfolding scenarios. Green arrows show smoothly raising “plateau” with a clear ~13–18 nm hump, potential intermediate state in FnIII domain. Green area highlights similar unfolding event of FNIII module with (top curve) and without (bottom curve) the hump. In the inset the average of 7 similar unfolding peaks (blue curve) with standard deviation (grey) is shown. Panels (b) and (c) present long “plateaus” (blue, yellow areas) proceeded by a partial unfolding of a single (b) or several (c) Ig domains. (d) Hypothetical structure of adsorbed native CNTN4 with a horseshoe conformation (light-blue box) (0), possible unfolding arrangements of CNTN4 with the horseshoe fold of IgC21–4 modules are shown in schemes (1) and (2).
