Figure 4
From: Molecular architecture of the Ub-PCNA/Pol η complex bound to DNA
The ubiquitin adopts the ‘flipped-out’ conformation to interact with the C-terminal domain of Pol η.
(a) The protomer of the native Ub-PCNA crystal structure in the extended conformation (light sea green; PDB ID 3TBL) and the SUMOK164-PCNAmono (magenta; PDB ID 3V61) are fitted into the EM map of the ternary complex. The crystal structure of the ubiquitin (yellow; PDB ID 1UBQ) is manually docked into the map to show its approximate position relative to the other crystal structures. (b) Top view of (a) with the EM map omitted for clarity. (c) The crystal structure of the PCNA bound to a 20-mer peptide carrying PIP-box of Pol η (PDB ID 2ZVK) is fitted to the same orientation within the EM map as in (a). Viewing direction is same as in (b). The PIP-box sequences are colored red. The proposed interaction between the UBZ of Pol η with ubiquitin is depicted. (d) Schematic representation of the overall ternary complex in two different orientations showing the interaction of the C-terminal domain of Pol η with only one of the conjugated ubiquitins on PCNA. Map segments corresponding to the C-terminal domain of Pol η and ubiquitin are colored dark green and yellow, respectively.
