FIGURE 3.

Pre-PHD zinc finger and PHD2 finger of PHF6 fold as an integrated structural module. A, overall view of PHF6-ePHD2 domain, with regions of interest in boxes. B, detailed interactions between the pre-PHD zinc finger and PHD2 finger of PHF6-ePHD2 domain, color scheme as for Fig. 1. Secondary elements are labeled accordingly. C, detailed hydrophobic interactions at the interface between the pre-PHD zinc finger and helix α3 and loop L1. D and E, network of hydrogen-bonding interactions between the pre-PHD zinc finger, helix α3, and PHD2 finger of the PHF6-ePHD2 domain. Water molecules are represented by red dots. The hydrogen bonds are displayed as red dashed lines. F, structural superposition of the pre-PHD zinc finger of the ePHD2 domain of PHF6 (shown in green, the only zinc ion is shown in orange) with the PHD1 finger of BRPF2 (shown in blue, two zinc ions are shown in gray). G, structure-based sequence alignment of the pre-PHD zinc finger of PHF6-ePHD2 with AIRE-PHD and BRPF2-PHD1 fingers. The conserved zinc-chelating residues are highlighted on an orange background, the absent zinc-chelating residues in a pink and the absent acidic residues in a gray background. Secondary structural elements of pre-PHD zinc finger of PHF6-ePHD2 and BRPF2-PHD1 finger are shown above and below the sequences, respectively.