Movie S2.

Ubiquitin/USP complex crystal structures. Six high-resolution (<2.4 Å) ubiquitin (pink)/USP (yellow) crystal structures are shown (1NBF:C/B, 1NBF:D/A, 2HD5:B/A, 2IBI:B/A, 3MHS:D/A, and 3NHE:B/A). Ubiquitin residues D52 and G53 are shown with a stick representation. Any USP residue within 10 Å of the D52-G53 peptide bond (colored red, white, and blue) is also shown with a stick representation. The Cα atoms of E24 and G53, which were mutated to Ala, are shown as spheres.