Bet v I allergen is a family

Protein family

A protein family is a group of evolutionarily-related proteins, and is often nearly synonymous with gene family. The term protein family should not be confused with family as it is used in taxonomy....

 of protein 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.

Trees within the order Fagales possess particularly potent allergens, e.g. the prototypical Bet v1, the major white birch (Betula verrucosa) pollen antigen. Bet v1 is the main cause of type I allergies observed in early spring. Type I, or immunoglobulin E-mediated (IgE-mediated) allergies affect 1 in 5 people in Europe and North America. Commonly-observed symptoms are hay fever, dermatitis, asthma and, in severe cases, anaphylactic shock. First contact with these allergens results in sensitisation; subsequent contact produces a cross-linking reaction of IgE on mast cells and concomitant release of histamine. The inevitable symptoms of an allergic reaction ensue.

Categorization

A nomenclature system has been established for antigens (allergens) that cause IgE-mediated atopic allergies in humans. 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.

The allergens in this family include allergens with the following designations: Bet v 1, Dau c 1, and Pru a 1. Other proteins belonging to this family include the major pollen allergens:

• Aln g I from Alnus glutinosa (Alder);
• Api G I from Apium graveolens (Celery);
• Car b I from Carpinus betulus (European hornbeam);
• Cor a I from Corylus avellana
  Corylus avellana
  Corylus avellana, the Common Hazel, is a species of hazel native to Europe and western Asia, from the British Isles south to Iberia, Greece, Turkey and Cyprus, north to central Scandinavia, and east to the central Ural Mountains, the Caucasus, and northwestern Iran. It is an important component of...
  
  (European hazel);
• Mal d I from Malus domestica (Apple).

Structure

NMR analysis has confirmed earlier predictions of the protein structure and site of the major T-cell epitope. The Bet v1 protein comprises 6 anti-parallel beta-strands and 3 alpha-helices. Four of the strands dominate the global fold, and 2 of the helices form a C-terminal amphipathic helical motif. This motif is believed to be the T-cell epitope.

The motif is also found in:

• the wound-induced protein AoPR1 from Asparagus officinalis (Garden asparagus);
• the pathogenesis-related protein
  Pathogenesis-related protein
  Pathogenesis-related proteins are proteins produced in plants in the event of a pathogen attack. They are induced as part of systemic acquired resistance.Many proteins found in wine are grape pathogen-related proteins...
  
  s from Phaseolus vulgaris (Kidney bean) and Petroselinum crispum (Parsley) (PR1-1 and PR1-3);
• the disease resistance response proteins, STH-2 and STH-21, from Solanum tuberosum (Potato) and pI49, pI176 and DRRG49-C from Pisum sativum (Garden pea);
• the P.sativum abscisic acid-responsive proteins ABR17 and ABR18;
• and the stress-induced protein SAM22 from Glycine max (Soybean).

Additionally, the core domain of Bet v1 founds or is part of a superfamily of domains called SRPBCC (START/RHOalphaC/PITP

Phosphatidylinositol transfer protein

Phosphatidylinositol transfer protein or priming in exocytosis protein 3 is a ubiquitous cytosolic domain involved in transport of phospholipids from their site of synthesis in the endoplasmic reticulum and Golgi to othercell membranes....

/Bet v1/CoxG/CalC) that include the StAR-related lipid-transfer (START) domain.