Comparison of SmTopoI_N65, EcTopoI_N67, and MtTopoI via multiple sequence alignment shows high degree of sequence identity and similarity, including the highly conserved active site. Identical residues are highlighted in red, similar residues are highlighted in yellow, catalytic tyrosine is indicated with a red dot, active site residues within 5 Å from catalytic tyrosine are indicated with blue dots, and the nine-residue loop extension seen in SmTopoI_N65 is indicated with a magenta bar.