Figure 3.

Fos–Jun heterodimers bind the AP-1 site in a preferred orientation. (A) Diagram of the effect of the orientation of Fos (black)–Jun (gray) heterodimer binding on the direction of DNA bending. The central C:G base pair is shown in cross-section along with the conserved arginine of Fos, which contacts the guanine. (B) The heterodimers indicated on the left consisting of the wild-type (WT) Fos118–211 and Jun225–334 proteins or mutant proteins containing a substitution of the conserved arginine in Jun (R273I) or Fos (R155I) were incubated with the probes indicated above the lanes and described in Fig. 2A containing a central C:G (M) or G:C (W) base pair. The complexes were analyzed on an 8% polyacrylamide gel. The relative mobilities of the complexes were plotted as a function of the separation between the centers of the AP-1 site and the intrinsic bend.