Mites are ubiquitous arthropods inhabiting nearly every type of ecosystem. Domestic mites, which include house dust mites and storage mites, are one of the major sources of indoor aeroallergens worldwide with house dust mites being the leading cause of allergic asthma and rhinitis. It is not the mites themselves that are the cause of allergy, but various proteins found in the mite’s fecal pellets, salivary secretions, cuticle sheds, and eggs that are allergy inducing. The International Union of Immunological Societies and the World Health Organization recognize 128 proteins produced by mites as being allergenic. Of these, Groups 1 and 2 are considered major allergens. However, studies suggest that it isn’t the protein alone that is responsible for allergy, but the small molecule ligands that bind them likely play a role in the disease process as well. The purpose of this research is to structurally characterize Group 2 allergens from all 8 mite species that are known to produce them using X-ray crystallography methods, and to study the small molecules that bind them. Novel methods of Group 2 allergen expression were used to purify Der f 2, Tyr p 2, and Blo t 2 with Der p 2 being purified using previously established methods. In silico studies as well as probe displacement assays were used to study the binding of 9 fatty acids (of varying carbon length and saturation) and cholesterol to the binding pocket of Blo t 2 and Der p 2. The computational studies suggest no binding to cholesterol for either protein. At the same time, these studies indicate that Blo t 2 may bind 7 of the 9 fatty acids tested, whereas Der p 2 may bind 8 of the 9 fatty acids. Initial probe displacement assays indicate binding of Blo t 2 to oleic and pinolenic acid with a possible higher affinity for pinolenic acid.
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