Lineage

Root
1. Class Alpha and beta proteins (a/b) [51349] (51349)

Fold

The "swivelling" beta/beta/alpha domain (52008)

3 layers: b/b/a; the central sheet is parallel, and the other one is antiparallel; there are some variations in topology
this domain is thought to be mobile in most multi-domain proteins known to contain it

Superfamily Children