AF093: Expansin and expansin-like

List allergens from this family:

Routes of exposure:
Include only IUIS approved allergens.

Biochemical properties

Expansins are ubiquitous plant cell wall glycoproteins that catalyze cell wall loosening during cell growth and other developmental processes [1]. They are typically 250-275 amino acids long. Phylogenetic analysis revealed the existence of four subfamilies designated α-expansins, β-expansins, expansin-like A, and expansin-like B. Sequence identity between members of different subfamilies is only 20-40%. Expansin structures consist of two domains preceded by a poorly conserved unstructured glycosylated N-terminal stretch. The N-terminal domain (Pfam:PF03330) folds into a six-stranded β-barrel stabilized by three disulfide bonds. It is also found in some bacterial and eukaryotic lipoproteins and belongs to a large superfamily characterized by a six-stranded double-psi beta barrel fold [2]. The C-terminal domain (Pfam:PF01357), adopts an immunoglobulin-like two-layered β-sandwich structure.

Allergens from this family

β-Expansins from grass pollen are a family of major allergens designated group 1 grass pollen allergens. In addition, there is a family of expansin-related minor grass pollen allergens (group 2/3) that lack the N-terminal expansin domain. Weak IgE cross-reactivity between allergens from the groups 1 and 2/3 was observed [3]. No expansins outside the grass family have been shown to be allergenic.



  1. Sampedro J, Cosgrove DJ:
    The expansin superfamily.
    Genome Biol 2005, 6, 242. [PubMed] [Full Text]
  2. Castillo RM, Mizuguchi K, Dhanaraj V, Albert A, Blundell TL, Murzin AG:
    A six-stranded double-psi beta barrel is shared by several protein superfamilies.
    Structure 1999, 7, 227-36. [PubMed]
  3. Andersson K, Lidholm J:
    Characteristics and immunobiology of grass pollen allergens.
    Int Arch Allergy Immunol 2003, 130, 87-107. [PubMed] [Full Text]


Links to Pfam

Family-defining Pfam domains (at least one of these domains is present in each family member):

Pfam domain Pfam clan
PF01357 Pollen allergen -
PF03330 Lytic transglycolase CL0199 Double Psi beta barrel glucanase

Links to Wikipedia


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