This family represents the conserved barrel domain of the 'cupin' superfamily [1] ('cupa' is the Latin term for a small barrel). This family contains 11S and 7S plant seed storage proteins, and germins. Plant seed storage proteins provide the major nitrogen source for the developing plant.

1: Cupins: a new superfamily of functionally diverse proteins that include germins and plant storage proteins. Dunwell JM; Biotechnol Genet Eng Rev 1998;15:1-32. PMID:9573603