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. Author manuscript; available in PMC: 2010 Jun 1.
Published in final edited form as: Curr Opin Struct Biol. 2009 Oct 5;19(6):683. doi: 10.1016/j.sbi.2009.09.001

Figure 2.

Figure 2

(A) The T7 RNAP in the 7-nt RNA intermediate complex is bound to both promoter and downstream DNA.4 The PBD has rotated by 40° away from the C-terminal domain, avoiding a steric clash with the transcript and allowing for 7 bp of heteroduplex to form in the active site.

(B, C) Promoter and PBD movements during the transition. (B) A view looking down onto the promoter bound to the PBD. A 40° rotation of the PBD away from the active site occurs around an axis that passes through a flexible loop of residues 198 to 204. The catalytic aspartic acid residues (D812 and D537) represent the active site. (C) The same view as in (B) without the PBD but showing the specificity loop, which also rotates.