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. 1997 May 13;94(10):4913–4918. doi: 10.1073/pnas.94.10.4913

Figure 1.

Figure 1

Charged residues on the amino-terminal side of the basic regions of Fos and Jun induce DNA bending. (A) Alignment of the basic regions of Fos and Jun. Residues substituted in the mutant proteins are indicated in boldface above and below the alignment. (B) Phasing analysis of selected combinations of wild-type and mutant proteins. Proteins containing the amino acid residues indicated above the lanes at positions adjacent to their basic regions were incubated with phasing analysis probes containing the M site described in Fig. 2, and the complexes were analyzed by PAGE. Each set of lanes contained probes in which the separations between the centers of the AP-1 site and the intrinsic DNA bend were 26, 28, 30, 32, 34, and 36 bp, respectively. All of the complexes were run on the same gel, but the lanes were rearranged for a more concise figure. The average mobilities of complexes from multiple experiments were normalized for differences in probe mobilities and plotted with standard deviations as a function of the separation between the centers of the AP-1 site and the intrinsic bend. (C) The relative DNA bend angles induced by all combinations between the mutant and wild-type proteins were plotted as a function of the net charge of amino acid residues adjacent to the basic regions. The charged amino acids were assumed to be fully ionized with formal charges of +1 and −1. In the vicinity of the DNA helix, these formal charges are likely to be modified by the local microenvironment (32). It is therefore possible that the absolute charges are shifted to more positive values. However, the relative charges of the various complexes are likely to remain the same. The standard bend induced by the wild-type proteins is encircled. Vertical bars indicate standard deviations or ranges (two cases) of the bend angles calculated based on independent experiments. A heterodimer containing four arginine residues at the positions examined did not bind to the AP-1 site, possibly because of the high local charge predicted for such a complex.

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