Figure 4. Comparison of the positions of the C-terminal domains of Pol I A12.2, Pol II Rbp9 and Pol III C11.
The positions of A12.2 (A), Rpb9 (B) or C11 (C) are shown in yellow for Pol I*, Pol II (Kettenberger et al., 2004) and Pol III (Hoffmann et al., 2015), respectively. While the ED2 is structurally more conserved (light sea green color), the ED1 in Pol II and Pol III are larger than the Pol I ED1 (red). The structure of the ED1 determines the binding mode of Pol I A12.2C and Pol II Rpb9C, while in Pol III the presence of C53 induces a different binding site for C11C far from the ED. The position of the N-terminal tail of the second largest subunit is also indicated for each polymerase, as well as the extension in the ED1 of Pol II and Pol III.