Bla g 2

Among such allergens, Bla g 2 is of particular importance, eliciting IgE responses in 58–70% of cockroach allergic patients. The X-ray crystal structure of Bla g 2 shows a bilobal fold typical of pepsin-like aspartic proteases, but Bla g 2 is enzymatically inactive due to amino acid substitutions in the catalytic site. The structures of both lobes are similar despite the low degree of the amino acid sequence homology (<15% identity). The presence of a zinc binding site and five disulfide bridges in Bla g 2 adds stability to the protein, thus favoring persistence of the allergen in the environment. Chronic exposure to low doses (<1 µg/g dust) of this stable cockroach allergen may explain the association between sensitization to Bla g 2 and asthma.