InterPro domain: IPR035506

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 of the first three letters of the genus; a space; the first letter of the species name; a space and an arabic number. In the event that two species names have identical designations, they are discriminated from one another by adding one or more letters (as necessary) to each species designation.

Proteins in this family belong to the Poa p (Poa pratensis or Kentucky bluegrass) IX and Phl p (Phleum pratense) VI allergen family, and include allergens with the following designations: Lol p 5, Pha a 5, Phl p 6, and Poa p 9. Phl p 5b has been shown to possess ribonuclease activity [ 1 ]. Grass pollen allergens are one of the major causes of type I allergies (including allergic rhinoconjunctivitis, allergic bronchial asthma and hayfever), afflicting 15-20% of a genetically predisposed population [ 2 ].

These allergens exhibit an entirely alpha-helical structure with a four-helical bundle topology [ 3 ].

This superfamily represents a domain found in different pollen allergen proteins and in uncharacterised proteins from Oryza sativa (rice) including OsI_031781 and OsI_030282.

1. Major allergen Phl p Vb in timothy grass is a novel pollen RNase. FEBS Lett. 363, 6-12
2. Nucleotide sequence analysis of three cDNAs coding for Poa p IX isoallergens of Kentucky bluegrass pollen. J. Biol. Chem. 266, 1204-10
3. Structure of the functional domain of the major grass-pollen allergen Phlp 5b. Acta Crystallogr. D Biol. Crystallogr. 58, 1175-81