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Am J Respir Crit Care Med. 2002 Feb 1;165(3):391-7.

Cockroach allergen Bla g 2: structure, function, and implications for allergic sensitization.

Author information

1
Asthma and Allergic Diseases Center, Department of Internal Medicine, University of Virginia Health System, Charlottesville, VA, 22903, USA. apomes@inbio.com

Abstract

Exposure to German cockroach (Blattella germanica) allergens is associated with the development of chronic respiratory diseases, especially asthma. The mechanism by which allergic patients develop specific immunoglobulin E (IgE) responses to environmental allergens is unknown. However, recent reports provided evidence that enzyme activity, especially proteolytic activity, was a major contributor to allergenicity. Bla g 2 is one of the most potent cockroach allergens (prevalence of IgE responses of 60 to 80%) and shows homology to the aspartic proteinase family of enzymes. We investigated whether the allergenicity of Bla g 2 was linked to its putative enzymatic function. A molecular model of Bla g 2, based on the high resolution crystal structures of pepsin and chymosin, showed that the overall three-dimensional structure of Bla g 2 was similar to that of aspartic proteinases with a well-defined binding pocket. However, critical amino acid substitutions in the catalytic triads and in the "flap" region of the molecule suggested that Bla g 2 was inactive and homologous to mammalian pregnancy-associated glycoproteins. This was confirmed experimentally by enzyme assay. The results show dissociation between enzymatic activity and allergenicity for Bla g 2 and suggest that other genetic and environmental factors are important determinants of sensitization.

PMID:
11818327
DOI:
10.1164/ajrccm.165.3.2104027
[Indexed for MEDLINE]

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