Electron microscopic single-particle analysis of purified full-length Nup170 and Nup170C. (A) Affinity-purified Nup170 was analyzed by SDS-PAGE and Coomassie staining (left; contaminated by FAS and indicated by an asterisk) and by EM (right). A charge-coupled device image overview electron micrograph of the negatively stained Nup170 is shown. (B) Class averages (top), corresponding reprojections of the final 3D model (middle), and surface representations of Nup170 in equivalent orientations (bottom) are shown. (C) Modeling the Nup170 sequence with its predicted β-strands (purple; residues 144 to 648) and α-helices (red; residues 890 to 1,460; loops bigger than 12 aa were omitted) according to Devos et al. (2006) into the 3D EM structure of the Nup170. The β-propeller and α-solenoid were manually fitted into the 3D shape of the crescent-shaped Nup170 molecule. The dashed line indicates a putative unstructured region between the β-propeller and α-solenoid domains, ∼240 aa in length, for which a secondary structural prediction was not obtained. (D) SDS-PAGE of the purified C-terminal domain of Nup170 (left) and comparison of representative class averages of Nup170C with a projection of Nup170 full-length at the same scale (right). Bars: (B) 4.5 nm (D) 2.9 nm.