AF045: Cupin superfamily
- Pfam domains
- PF00190: Cupin
- PF04702: Vicilin N terminal region
The cupins are a large and functionally immensely diverse superfamily of proteins that have a common origin and whose evolution can be followed from bacteria to eukaryotes including animals and higher plants . These proteins share a β-barrel structural core domain to which the term cupin (derived from the Latin word cupa for barrel) was given. Cupins can be divided into single-domain cupins and two-domain bicupins. Monocupins include bacterial carbohydrate isomerases and epimerases, metal-dependent dioxygenases as well as germins and germin-like proteins. The largest families of bicupins are the 7/8S and 11S seed storage globulins that are the major components of plant seeds and constitute important protein sources of the human diet.
Allergenic members of the cupin superfamily belong to the seed storage globulins. These proteins are major food allergens from legumes, nuts and seeds . Seed storage globulins can be grouped into two families:
- 7/8S globulins (vicilins) are homotrimeric proteins of about 150 to 190 kDa. Their detailed subunit compositions vary considerably due to differences in proteolytic processing and glycosylation of the monomers. Allergenic vicilins include Ara h 1 from peanut, Jug r 2 from walnut, and Ses i 3 from sesame.
- Mature 11S globulins (legumins) are hexameric proteins that are initially assembled as intermediate trimers. In the protein storage vacuole, the subunits of the trimers are proteolytically processed to yield an acidic 30-40 kDa polypeptide linked by a disulfide bond to a basic polypeptide of about 20 kDa. Cleavage is accompanied by the transformation of two trimers into a mature hexameric 11S globulin. Allergenic legumins include the minor peanut allergen Ara h 3, soybean glycinin, Ber e 2 from Brazil nut, and Fag e 1 from buckwheat.
Cupins: the most functionally diverse protein superfamily?
Phytochemistry 2004, 65, 7-17. [PubMed]
Structural, biological, and evolutionary relationships of plant food allergens sensitizing via the gastrointestinal tract.
Crit Rev Food Sci Nutr 2004, 44, 379-407. [PubMed]
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