The VIN3 PHD superdomain is positively charged.A, molecular surface representation of Pd VIN3123-326 showing electrostatic surface potential (red, negative; blue, positive), with highly conserved (white) and variable (gray) positively charged residues labeled. B and C, electrostatic surface potential as in (A), of canonical PHD fingers binding to H3K4me2 histone H3 peptides, with conserved negatively charged residues lining the histone H3-binding pockets labeled. B, PHDPYGO1 (PDB code 2VPE); (C) ZnF-PHDUHRF1 (PDB code 3SHB); stick representations, histone H3 peptides (yellow). PDB, Protein Data Bank.