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. 2019 Mar 27;47(9):4721–4735. doi: 10.1093/nar/gkz213

Figure 1.

Figure 1.

The structural and kinetic illustrations of the T7 RNAP elongation cycle. (A) Crystal structures of the T7 RNAP elongation complexes. In the left panel, the RNAP subdomains are colored red for the ‘palm’, green for the ‘thumb’, dark blue for the ‘fingers’ of the hand-like structure, and magenta for the N-terminal. The DNA template strand and RNA are shown in cyan and blue, respectively. The sequence regions of the respective subdomains are also given. In the right panel, an alignment between the pre-insertion structure (PDB 1S0V, non-transparent) (20) and the substrate insertion structure (PDB 1S76, transparent) (32) of T7 RNAP is provided, in a zoom-in view around the active site. An illustration of the O-helix rotation angle is provided, with the O-helix open in the pre-insertion state, and closed in the insertion state. (B) A kinetic scheme of the NAC of T7 RNAP. The NTP insertion process from the initial pre-insertion state (III) to the final substrate insertion state (IV) is our focus in this work.