Fold: Double-stranded beta-helix

one turn of helix is made by two pairs of antiparallel strands linked with short turns
has appearance of a sandwich of distinct architecture and jelly-roll topology

Lineage:

1. Root: scop
2. Class: All beta proteins
3. Fold: Double-stranded beta-helix
   one turn of helix is made by two pairs of antiparallel strands linked with short turns
   has appearance of a sandwich of distinct architecture and jelly-roll topology

Superfamilies:

1. RmlC-like cupins (6)
2. Clavaminate synthase-like (6)
   Iron and ketoglutarate-dependent enzymes; elaborated version of this common fold
3. cAMP-binding domain-like (2)
4. Regulatory protein AraC (1)
5. Thiamin pyrophosphokinase, substrate-binding domain (1)
6. Calcium ATPase, transduction domain A (1)
   a distorted variant of double-helix
7. Trp RNA-binding attenuation protein (TRAP) (1)
   shorter variant of double-helix