Figure 1.

FosB/JunD bound to cognate DNA. (A) bZIP domain with leucine zipper and DNA binding regions (top). Only the d-position residues are displayed for Heptad 2–5 for simplicity. Consensus motif NxxAAxxCR in human AP-1 and ‘AP-1-like’ bZIP domains binds DNA (bottom). For emphasis, FosB C¹⁷² and its counterparts are highlighted in golden, while FosB R¹⁷⁶ and its counterparts are highlighted red (Arg) or blue (Lys) respectively. (B) FosB/JunD bound to an AP-1 site (FJ-DNA type I), front and side view. Leucines at the d-positions are shown. C¹⁷² (FosB) and C²⁸⁵ (JunD) are depicted as yellow spheres. (C) Consensus motif (NxxAAxxCR) of FosB (Motif-F, N¹⁶⁵-R¹⁷³; top) and JunD (Motif-J, N²⁷⁸-R²⁸⁶; bottom) bound to palindromic AP-1 DNA. Bases in contact with protein residues are colored (G: green; T: brown and C: cyan). The closest key contacts (< 5Å) between side chains and bases are shown as dashed lines. C¹⁷² (FosB) occupies alternate conformations. (D) Distance between the thiol groups of C¹⁷² (FosB, conformer A) and C²⁸⁵ (JunD). (E) Helical wheel indicating the locations of C¹⁷² (FosB) and C²⁸⁵ (JunD). Color scheme for (B–D) is displayed at the upper-left corner of B (FosB: red; JunD: blue; DNA: grey; Motif-F: lilac; Motif-J: light green). Non-carbon atoms in red (oxygen), blue (nitrogen), and yellow (sulfur).