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. 2021 Mar 3;49(6):3109–3126. doi: 10.1093/nar/gkab130

Figure 1.

Figure 1.

Structure of the capping enzyme GTase domain and its interactions with RNA Pol II CTD. (A) Structure of the human GTase domain (PDB ID: 3S24) (10) with one RNA Pol II CTD heptad (shown as sticks) bound in the conformation as resolved in the mouse GTase–CTD complex by Ghosh et al. (PDB ID: 3RTX) (32). Three subdomains of the GTase are labelled and coloured in green (NT), orange (OB) and blue (Hinge). GTP and Mg2+ (shown as spheres) were modelled in representative binding poses of the first enzymatic step and indicate the location of the active site. Important secondary structural elements are labelled following assignment in Chu et al. (10). (B) The GTase–CTD interface displaying the previously identified CTD interaction sites on the GTase: a pSer5 charged pocket (CDS1, composed of R330, K331 and R386) and a Tyr1 interaction site (CDS–Y1, composed of F367, V372, C383 and E387). The pSer2 group is solvent exposed and forms no interactions with the GTase residues. (C) Electrostatic potential surface of the human CE GTase. Positively charged regions (blue) have the potential to form additional pSer interaction sites. The pSer interaction sites discussed in this work—CDS1 and a novel site CDS2—are labelled.