Fold: T-fold

beta(2)-alpha(2)-beta(2); 2 layers: alpha/beta; antiparallel sheet 1234
tunnel-shaped: its known members form wide oligomeric barrels different sizes

Lineage:

1. Root: scop
2. Class: Alpha and beta proteins (a+b)
   Mainly antiparallel beta sheets (segregated alpha and beta regions)
3. Fold: T-fold
   beta(2)-alpha(2)-beta(2); 2 layers: alpha/beta; antiparallel sheet 1234
   tunnel-shaped: its known members form wide oligomeric barrels different sizes

Superfamilies:

1. Tetrahydrobiopterin biosynthesis enzymes-like (4)
   bind purine or pterin in topologically similar sites between subunits
   1. GTP cyclohydrolase I (2)
   2. 6-pyruvoyl tetrahydropterin synthase (1)
   3. DHN aldolase/epimerase (2)
      beta-sheets of four subunits form a barrel, closed: n=16, S=16
   4. Urate oxidase (uricase) (1)