Fold: DNA breaking-rejoining enzymes

core: alpha3-beta3-alpha4; one side of beta-sheet is exposed

Lineage:

1. Root: scop
2. Class: Alpha and beta proteins (a+b)
   Mainly antiparallel beta sheets (segregated alpha and beta regions)
3. Fold: DNA breaking-rejoining enzymes
   core: alpha3-beta3-alpha4; one side of beta-sheet is exposed

Superfamilies:

1. DNA breaking-rejoining enzymes (2)
   1. Lambda integrase-like, catalytic core (5)
   2. Eukaryotic DNA topoisomerase I, catalytic core (2)