Fig. 1.
Conformational changes in the promoter DNA during the initiation and the transition from initiation to elongation. The distance between the donor and the acceptor in the free promoter DNA is relatively large (A) and is shortened in the initiation complexes IC2–4 because of sharp bending (B). It is further shortened as IC2–4 changes to IC4–7 because of DNA bending, scrunching (in blue dotted region), and rotation (dotted curved arrow) changes (C). The conversion of IC to EC significantly reduces DNA bending that increases the D–A distance (D).