NOVEL ALLERGEN STRUCTURES WITH TANDEM AMINO-ACID REPEATS DERIVED FROMGERMAN AND AMERICAN COCKROACH

Cockroaches produce potent allergens that are an important cause of as thma. The two principal domiciliary cockroach species, Blattella germa nica and Periplaneta americana, secrete major allergens, Bla g 1 and P er a 1. Here, we report the molecular cloning of three Bla g 1 cDNA cl ones, which showed 70% amino acid sequence identity with Per a 1. Plaq ue immunoassays with human IgE antibodies or murine monoclonal antibod ies showed that these allergens were antigenically cross-reactive. The Bla gl sequences also showed homology to five previously undefined co ckroach allergen sequences. An unusual feature of all these sequences was that they contained multiple tandem amino acid repeats of similar to 100 amino acid residues. Between one and seven repeat units were id entified by dot-plot matrix analysis. The sequences also showed homolo gy to a mosquito protein involved in digestion (ANG12 precursor) and t o mitochondrial energy transfer proteins. High levels of Bla g 1 were found in cockroach hindgut and proventriculus. Amino acid sequencing o f natural Ela g 1 and Per a 1 suggested that these allergens are cleav ed by trypsin-like enzymes following secretion into the digestive trac t. The repeat sequences appear to have evolved by duplication of an an cestral amino acid domain, which may have arisen from the mitochondria l energy transfer proteins.