FIGURE 1.
Crystal structure of T. thermophilus Cas3HDdom. A, unbiased Fo − Fc electron density map contoured at 3σ. The residues, which are represented as sticks, were omitted from the map calculation. B, ribbon trace of the Cas3HDdom structure. The HD domain motifs are colored as follows: motif I (red), motif II (green), motif III (orange), motif IV (blue) and motif V (pink). The black sphere represents the cognate metal binding site. The N and C termini are labeled. C, Amino acid sequence conservation scores mapped onto the surface of two orthogonal views of the Cas3HDdom using CONSURF (41). The structure to the left is in the same orientation as shown in B. The conservation scale is drawn below the two views of the structure. The black sphere represents the cognate metal-binding site. D, Cas3HDdom metal ion-binding site. Residues colored by element are in the metal ion-bound configuration. Residues colored yellow are in the protein alone configuration. The Ni2+ (blue) and two water molecules (red) are represented as spheres. Anomalous difference electron density map contoured at 5σ (white mesh) reveals the site of the Ni2+ ion.