FIGURE 7.
Structures of the capping apparatus from S. cerevisiae and bluetongue virus and a complex between the phosphorylated RNAP II CTD and C. albicans guanylyltransferase. (a) Structure of a complex between S. cerevisiae Cet1 and Ceg1. The Cet1 homodimer is shown with Cet1 protomers colored cyan and magenta. The Ceg1 NTase domain is colored blue and OB domain is colored yellow. Dashed lines indicate disordered amino acids. The Cet1 WAQKW motifs are represented in ball-and-stick and specified amino acid side chains are labeled. Lys70 is shown in Ceg1 to indicate the position of the guanylyltransferase active site. (b) Structure of bluetongue virus VP4 (PDB 2HJA) in ribbon representation indicating the following domains: kinase-like (KL; gold), N7-methyltransferase (N7 MTase; green), 2′-O methyltransferase (2′-O MTase; gray), and triphosphatase/nucleotidyltransferase (TPase/NTase; blue). GpppG shown in the 2′-O MTase active site with S-adenosyl-homocysteine (AdoHcy, PDB 2HJP) shown in both N7 and 2′-O MTase active sites in stick representation. Dashed lines indicated disordered regions. (c) The structure of C. albicans Cgt1 (PDB 1P16; chain B) with NTase (blue), OB domain (yellow) bound to a Ser5 phosphorylated RNAP II CTD peptide (green). Close-up view of the CTD binding site with positions for Tyrosine 1, Proline 3, and phosphorylated Ser5 indicated. The CTD and GTP in the active site shown in stick representation. Dashed lines denote disordered regions.