COMPARATIVE-ANALYSIS OF THE GENES ENCODING GROUP-3 ALLERGENS FROM DERMATOPHAGOIDES-PTERONYSSINUS AND DERMATOPHAGOIDES-FARINAE

Group 3 allergens of the genus Dermatophagoides represent one of the m ajor groups of house dust mite allergens. The cDNA sequence data for D er p 3, in combination with both N-terminal amino acid sequences and s ubstrate affinity data, have confirmed that the group 3 allergens are trypsin-like proteases. Using the information from the Der p 3 P3WS1 c DNA clone, genes encoding both Der f3 and Der p 3 have now been amplif ied by the polymerase chain reaction and analysed. Two Der f3 clones a nd three Der p 3 genomic clones were sequenced. Each of the clones con tained a single small intron and encoded a mature protein of 233 amino acids. The nucleotide sequence was identical for both Der f3 clones. There was 81% identity between the Der f3 sequence and the original De r p 3 P3WS1 clone. The calculated molecular weight of Der f3 was 25.27 kDa compared to 24.98 kDa for Der p 3. All the amino acid residues re quired for the catalytic activity and the substrate specificity were c onserved between the two homologues. The coding sequences of two of th e three Der p 3 genomic clones were identical to the original Der p 3 P3WS1 clone with the third having nucleotide changes resulting in four non-conservative amino acid substitutions in the mature protein. Thes e substitutions resulted in a molecule with a slightly larger molecula r weight and a more acidic pi value than the original Der p 3 clone. T his third Der p 3 genomic clone is, therefore, an isoform of the Der p 3 P3WS1 clone and is classified as an isovariant of the allergen. The nucleotide sequence data presented are the first reported for Der f3. The Der f3 gene, like the Der p 3 gene, encoded a trypsin-like protea se, but with a slightly larger molecular weight.