Figure 1.

The conserved structural core of His-Me finger fold of Cas9 (PDB ID: 4ogc). The core elements are coloured in yellow and blue for β-strands and α-helix, respectively. The catalytic histidine is shown as red sticks. The remaining HNH sequence motif residues are shown as green sticks. The residues from outside the motif, chelating catalytic zinc ion (orange), are denoted as grey sticks. The sequence logo was generated based on the structure-guided multiple sequence alignment of all superfamily sequences clustered at 70% sequence identity using the Skylign server (106). The total height of the letters depicts the information content of the position in bits.