Fig. 2.

Locations at which Imp-α/CAS complexes assemble and disassemble during nuclear import (Left) and export (Right). (Left) Trajectories from nuclear import assays (as in Fig. 1 A–C) in which Imp-α (donor dyes) interacted with CAS (acceptor dyes) and did not dissociate from CAS. (Upper) Those trajectories in which Imp-α ended up in the nucleus (productive transport); (Lower) those trajectories in which Imp-α ended up returning back to the cytoplasm (abortive transport). The positions of CAS-free Imp-α are indicated by blue open circles, and the positions of Imp-α/CAS complexes, as determined by smFRET, are identified by purple solid circles. The black solid circles identify the first location at which FRET was observed (n = 50 and 20, Upper and Lower, respectively). (Right) Trajectories from nuclear export assays of Imp-α/CAS complexes (as in Fig. 1 D–F) in which the Imp-α/CAS complexes dissociated at the NPC. (Upper) Those trajectories in which Imp-α ended up in the cytoplasm (productive transport); (Lower) those trajectories in which Imp-α ended up returning back to the nucleus (abortive transport). The positions of Imp-α/CAS complexes, as determined by smFRET, are indicated by solid purple circles, and the positions of CAS-free Imp-α are identified by blue open circles. The black solid circles identify the last location at which FRET was observed (n = 31 and 20, Upper and Lower, respectively). The orange dashed lines identify the location of Imp-α/CAS complex assembly in the nuclear basket (Left) and Imp-α/CAS complex disassembly in the cytoplasmic filament region (Right). For scale, the green and black lines are −100 and +100 nm from the NE. For all panels, trajectories from multiple NPCs were aligned and overlaid.