Bet v 1-related proteins are widely distributed among vascular plants. The family was classified by sequence similarity into two large and several small subfamilies showing low levels of sequence identity but conserved structures . The largest of these is the pathogenesis-related protein family PR-10 . The expression of these proteins is either induced by pathogen attack or abiotic stress or developmentally regulated. PR-10 proteins are expressed in high concentrations in reproductive tissues such as pollen, seeds and fruits. The biochemical function of most PR-10 proteins is unknown. For some PR-10 subfamily members an enzymatic function as ribonuclease  or oxidative coupling enzyme involved in biosynthesis of secondary metabolites was shown . Like all members of the Bet v 1-family, PR-10 proteins contain a large ligand-binding cavity that can accommodate diverse ligands including plant steroids , cytokinins  and flavonoids . The other large subfamily is a group of major latex proteins and ripening-related proteins (MLP/RRP) first described in the latex of opium poppy . Their biologic function is unknown, but they appear to have a role in defense against biotic and abiotic stress .
The major birch pollen allergen, Bet v 1, is a member of the PR-10 family. Closely-related, cross-reactive allergens were found in the pollen of other trees from the order Fagales such as hazel, alder, oak and chestnut. Many birch pollen-allergic patients show allergic reactions to various fruits and vegetables, which are caused by IgE cross-reactivity between Bet v 1 and homologous allergens from plant foods . Most Bet v 1-related food allergens were found in members of certain plant families: Rosaceae (apple, pear, stone fruits), Apiaceae (celery, carrot), and Fabaceae (soybean, peanut). Only two Bet v 1-related allergens were identified outside the PR-10 subfamily. Vig r 6 is a minor allergen from mung bean and member of the cytokinin-specific binding proteins subfamily, a small subfamily distantly related to the PR-10 group . Act d 11 is a minor kiwifruit allergen belonging to the MLP/RRP subfamily .
Family-defining Pfam domains (at least one of these domains is present in each family member):
|Pfam domain||Pfam clan|
|PF00407||Pathogenesis-related protein Bet v I family||CL0209||Bet V 1 like|
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