Figure 2.

Cryo-EM structure of mammalian Pol II EC bound by α-amanitin. A, nucleic acid scaffold is depicted schematically. Filled and unfilled circles represent modeled and not modeled nucleotides, respectively. The nucleotide-binding site (red dashed circle), bridge helix (green), the catalytic metal ion A (pink), trigger loop (brown), and α-amanitin (orange) are indicated. The color code is used throughout. B, overview of the structure. Pol II is shown as a silver ribbon model, and other elements are colored as in A. C, electron density for α-amanitin (orange mesh) in three different views. Important contact moieties with Pol II are indicated. Nitrogen, oxygen, and sulfur atoms are blue, red, and yellow, respectively.