Figure 2. The Nup107/Nup133 Complex Structure.

(A) Overall structure of the Nup107_658–925/Nup133_934–1156 interaction complex. Nup107 is colored in blue, Nup133 in orange. Both proteins are entirely α-helical and interact via a compact interface, mainly involving two helices from each binding partner. Secondary structure elements in Nup107 are labeled (helices α4 and α8 of Nup107 are obscured and labels omitted for clarity). Nup107 forms an irregular stack of helices, with helix 6 protruding noticeably from the domain core. (B) Overall structure rotated by 90° compared to (A). Helices in Nup133 are numbered. Nup133 consists of two connected domains, an interacting 4-helix bundle and the C-terminal domain. (C) Schematic domain organization of Nup107 and Nup133. Important residue positions are indicated. α-helical domains are marked in grey outside of the crystallized regions which are colored in blue and orange, respectively. The β-propeller domain (PDB code 1XKS) is colored white. (D) Superposition of the Nup107_658–925/Nup133_934–1156 interaction complex crystallized in two different crystal forms, shown as tubes. In the protein construct used in crystal form 2 the helix 6 protrusion is replaced by a short flexible linker. Tube thickness proportional to temperature factors, indicating flexibility. The C-terminal helical domain of Nup133 is significantly more flexible than the rest of the protein and shows rigid body movement.