Acid-induced polymerization of the group 5 mite allergen from Dermatophagoides pteronyssinus

House dust mites are the most important source of indoor allergens and caus e allergic diseases. Our studies here suggest that the group 5 allergen fro m Dermatophagoides pteronyssinus (Der p 5) is monomeric at neutral pH, but forms filaments at low pH. Circular dichroism measurements show Der p 5 is a helical protein, and the protein sequence reveals Der p 5 contains coiled -coil helices. The acid-induced filament assembly could be explained in par t by the high content of charged residues (40%) in the coiled-coil structur e. Interestingly, some of the known Dermatophagoides allergens also contain a heptad repeat, which could potentially form coiled coils. Therefore, coi led-coil helices may be one of the common structural motifs of mite allerge ns that contribute to their allergenicity. (C) 2001 Academic Press.