Figure 3.

Structure of SETD3 in complex with Met⁷³ in the active site. A, a surface representation of SETD3 (colored gray) accommodation of Met⁷³ peptide in a long surface groove. Omit electron density for ordered residues 66–84 (in stick model) is contoured at 3σ above the mean. B, superimposition of SETD3 in complex with Met⁷³, Lys⁷³, and methylated His⁷³. C, omit electron density (F_o − F_c) for Met⁷³ contoured at 4σ above the mean. D, the Met⁷³ side chain and the methionine moiety of SAH is nearly symmetric to each other by a rotation of 180°. E, the nonpolar S-methyl thioether side chain is in contact with aromatic and hydrophobic residues. F, a C–H···O hydrogen bond is formed between the main chain Cα atom of Met⁷³ of actin and side chain of Asn²⁵⁵ of SETD3. G and H, SETD3 N255V and N255A mutants have high activity on Met⁷³. I, superimposition of SETD3 (N255) (PDB code 6WK1) and its mutant N255V (PDB code 6WK2) in complex with actin Met⁷³ peptide. J, electron density (2F_o − F_c) for Val²⁵⁵ contoured at 2.0σ above the mean.