FIGURE 2.

The solution structure of sRbx1^12–108. A, superposition of the 20 lowest energy structures of sRbx1^12–108 (residues 40–108, shown in gray) is shown. The N terminus of sRbx1^12–108 (residues Gly-12–Val-39, magenta) is shown for five structures to demonstrate its disordered state. B, a ribbon structure of sRbx1^12–108 shows helices α1 (Cys-53–Ala-58) and α2 (Phe-81–Thr-90) and β-sheets β1 (Val-70–Gly-73) and β2 (His-77–His-80). The coordinating residues for the three Zn²⁺ binding sites in sRbx1^12–108 are shown in yellow. C, shown is the crystal structure of Rbx1/ROC1 bound to the C-terminal domain of cullin1 (PDB 1LDJ) (7). In contrast to A, the N terminus of Rbx1/ROC1 forms an intermolecular β-sheet (magenta) used in the recruitment of Rbx1/ROC1 to the cullin proteins. All structures were created using PyMol (64).