Figure 1. Comparison of TF1 and BstHU structures.

(A) Energy minimized model of TF1 (1WTU) in complex with DNA derived from the IHF-DNA structure (1IHF). Lys³, shown to contact DNA 8–9 bp distal to the DNA kinks [23] is indicated in red, and the DNA-intercalating Pro⁶³ is shown in orange. (B) Lys³ (red) forms a salt bridge with Asp²⁶ (orange) in B. stearothermophilus HU (1HUE). (C) Expanded view of TF1 salt bridge between the ϵ-amino group of Lys³ and phosphate oxygen of the DNA backbone. (D) Expanded view of the surface salt bridge between Lys³ and Asp²⁶ of BstHU. In (C, D), nitrogen is coloured blue, oxygen is red, carbon is grey, and phosphorous is orange. Expanded views are identified in (A, B) by a black frame.