Fig. S1.

Ubv libraries. (A) Regions 1, 2, and 3 targeted in the library designs are shown. Only positions relevant to the library design are included and residues that differ from WT Ub sequence are highlighted in gray. Positions subjected to soft-randomization are boxed and positions subjected to complete randomization are indicated by an “X”. (B) Skp1tr–F-box^Fbw7–Ubv.Fw7.1 complex showing Ub positions diversified in the libraries. Regions 1, 2, and 3 are shown in separate panels and targeted positions are shown as salmon spheres and numbered. Skp1tr, F-box^Fbw7, and Ubv are colored green, orange, or blue, respectively. Loop1 deleted in Skp1tr is labeled and colored magenta.