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. 2008 Oct 9;105(42):16101–16106. doi: 10.1073/pnas.0802647105

Fig. 4.

Fig. 4.

Single-molecule force measurements between importin-β and the NPC. The NE was isolated from Xenopus laevis and imaged by AFM in contact mode in liquid. (A and B) The cytoplasmic side (A) and the nucleoplasmic side (B) of the NE were observed. The enlarged images are shown in the Insets. (Scale bars, 500 nm.) (C–E) The same specimen was used to measure the interaction with importin-β. The cantilever used for the imaging was switched to the cantilever carrying full-length importin-β, and then the force measurement was performed with the nucleoplasmic side (C) and the cytoplasmic side of the NE (E). Some of the Nups contain Ran binding site(s) (38–40), although the effect of Ran binding to these Nups on the NPC function is still unknown. To avoid effects, if any, of Ran on the NPC function and/or structure, the importin-β-attached cantilever was first incubated with RanGppNHp, and then the force measurement was performed against the nucleoplasmic side of the NE in the Ran-free solution (D). The rupture force is summarized in the histogram. The histograms were fitted with Gaussian distribution. The peak values (f) are also indicated in the histogram.