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Figure 2
Conformation of the isopeptide bond in the crystal structure of Ub2. (a) Cross-eye stereoview of the σA-weighted 2Fo − Fc electron-density map at the isopeptide linkage contoured in blue at 0.35 e Å−3. The atomic model is drawn as sticks. Water molecules are drawn as red spheres. (b) The three Lys48-linked Ub2 molecules in one asymmetric unit are coloured yellow for chains A–B, blue for chains C–D and red for chains E–F. Distal (A, C and E) and proximal (B, D and F) ubiquitin moieties are distinguished by pale and dark shades, respectively. Chains C′ and D′ are from an adjacent asymmetric unit and are labelled in pale and dark cyan, respectively. The isopeptide linkages are shown as spheres coloured by atom type (white, carbon; blue, nitrogen; red, oxygen). (c) Cross-eye stereoview of the isopeptide bond and its interactions. Residues labelled with primes belong to a distal moiety. Hydrogen bonds are shown as dashed lines. C atoms of chains A–B and E–F are shown in yellow and salmon red, respectively. |
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