Figure 12.

DNA-binding by IHF and T7 endonuclease I. (a) In the IHF-DNA complex (PDB code 1IHF) the DNA is roughly bent, with proline residues (red) intercalating, destacking the base pairs and stabilising the kinked structure. No direct or indirect contacts of IHF with the DNA major groove can be observed; (b) Illustration of a Holliday junction bound by T7 Endonuclease I (PDB code 2PFJ). The protein-DNA interactions results in large conformational changes: the duplex arms of the Hj are kinked by 80° and the junction centre is opened.