This architecture is formed from a capped beta barrel with an internal pseudo threefold symmetry.
The examples shown below are the agglutinin domain (CATH domain ID 1jlxA01), and acidic fibroblast growth factor (FGF-1) (CATH domain ID 1afcA00).
J Mol Biol133p557-63(1979 Oct 9)
Murzin AG, Lesk AM, Chothia C
J Mol Biol223p531-43(1992 Jan 20)