Fold: Acid proteases

barrel, closed; n=6, S=10, complex topology

Lineage:

1. Root: scop
2. Class: All beta proteins
3. Fold: Acid proteases
   barrel, closed; n=6, S=10, complex topology

Superfamilies:

1. Acid proteases (2)
   1. Retroviral protease (retropepsin) (7)
      dimer of identical mono-domain chains, each containing (6,10) barrel
   2. Pepsin-like (20)
      duplication: consists of two similar barrel domains
      N-terminal: barrel, partly opened; n*=6, S*=10