- A: beta complex topology
- X: Beta-strand domain in eukaryotic DNA topoisomerase I, N-terminal DNA-binding fragment
- H: Beta-strand domain in eukaryotic DNA topoisomerase I, N-terminal DNA-binding fragment
- T: Beta-strand domain in eukaryotic DNA topoisomerase I, N-terminal DNA-binding fragment
- F: Topoisom_I_N