Fig. 2. DNA structures built from eight 20-nt strands of four-way DNA junction (at the center) were checked for HU binding. HU protein at concentrations indicated in nM was mixed with labeled DNA in a buffer containing 200 mM NaCl, and bound and free DNA were gel-separated. (A) ss-fork; (B) ds-fork; (C) three-way junction; (D) four-way junction with an ss-branch; (E) four-way junction with a nick. For HU binding to other DNA structures indicated here see Figure 1.