InterPro domain: IPR000617

Napins are low-molecular weight, basic storage proteins synthesised in rape-seed embryos during seedmaturation [ 1 , 2 ]. Sequence comparisons have revealed that napin belongs to a diverseprotein family, which includes major allergens, trypsin inhibitors and natural anti-fungal proteins. Napincomprises 2 polypeptide chains (MW 9000 and 4000) held together by disulphide bonds. The protein isinitially synthesised as a precursor of 178 residues, which is proteolytically cleaved to generate maturenapin chains, with 86 and 29 residues respectively.

Some of the proteins in this family are allergens. Allergies are hypersensitivity reactions of the immune system to specific substances called allergens (such as pollen, stings, drugs, or food) that, in most people, result in no symptoms. A nomenclature system has been established for antigens (allergens) that cause IgE-mediated atopic allergies in humans [WHO/IUIS Allergen Nomenclature Subcommittee King T.P., Hoffmann D., Loewenstein H., Marsh D.G., Platts-Mills T.A.E., Thomas W. Bull. World Health Organ. 72:797-806(1994)]. This nomenclature system is defined by a designation that is composed ofthe first three letters of the genus; a space; the first letter of thespecies name; a space and an arabic number. In the event that two speciesnames have identical designations, they are discriminated from one anotherby adding one or more letters (as necessary) to each species designation.

The allergens in this family include allergens with the following designations: Bra j 1.

1. Structure of the rapeseed 1.7 S storage protein, napin, and its precursor. J. Biol. Chem. 261, 14576-81
2. cDNA clones for Brassica napus seed storage proteins: evidence from nucleotide sequence analysis that both subunits of napin are cleaved from a precursor polypeptide. J. Mol. Appl. Genet. 2, 273-83