Fig. 1: hRpn13 Pru crystallizes with a U-shaped peptide in its proteasome-binding site.

a Ribbon diagram of neighboring hRpn13 Pru molecules within the asymmetric unit cell displayed as a black box with the unit cell dimensions denoted. Additional density between the two molecules is displayed as a black mesh. b Comparison of the structure of hRpn2 (green with oxygen and nitrogen in red and indigo, respectively)-bound hRpn13 (gray with the β6-β7 loop in black, PDB 6CO4) and apo hRpn13 from this study (purple) showing the additional density (gray mesh) at the hRpn2 binding surface. c Superimposition of apo hRpn13 Pru structures from a previous study (colored as in panel b) with DTT present (5IRS) and from this study (purple). DTT (cyan with oxygen and sulfur in red and yellow, respectively) is bound to C88 and overlaps with the additional density (gray mesh) observed in this study. d Enlarged region of the hRpn13:ENT structure with hRpn13 displayed as a purple cartoon and stick rendering for ENT with each amino acid labeled within the 2Fo-Fc electron density map contoured at 1.6 σ (gray mesh). The native and non-native ENT amino acids are displayed in orange and yellow, respectively. e Structural overlay with hRpn13 Pru superimposed for its complex with hRpn2 (green with hRpn13 in black, PDB 6CO4) or ENT (colored as in d) with the β6-β7 loop indicated. f Cartoon of DTT bound to hRpn13 Pru C88 with the terminal ends disordered (left) or of hRpn13 Pru interaction with the N-terminal ENT residues (right).