Figure 1.

Schematic diagram of the NTP binding pathway. (A) Cross section of the T7 RNAP-ATP complex. NTP diffuses through a secondary channel of T7 RNAP before binding to the active site. The purple dashed arrow denotes the pathway of NTP binding defined in this work, which connects the “NTP-Out” and “NTP-BP” positions. (B) Front view of the funnel region in the “NTP-Out” state. The (Mg-ATP)²⁻ complex is placed in the middle position of the secondary-channel entrance. To see this figure in color, go online.