Fold: DNA clamp

contains two helices and two beta sheets
duplication: fold has internal pseudo two-fold symmetry

Lineage:

1. Root: scop
2. Class: Alpha and beta proteins (a+b)
   Mainly antiparallel beta sheets (segregated alpha and beta regions)
3. Fold: DNA clamp
   contains two helices and two beta sheets
   duplication: fold has internal pseudo two-fold symmetry

Superfamilies:

1. DNA clamp (2)
   1. DNA polymerase III, beta subunit (1)
      duplication: consists of three domains of this fold
   2. DNA polymerase processivity factor (6)
      duplication: consists of two domains of this fold