Homology modeling and monoclonal antibody binding of the Der f 7 dust mite allergen

Abstract

The group 7 allergens are important allergenic specificities for mite-sensitive patients and may need to be incorporated into new diagnostic and therapeutic strategies. However, little is known about their biological and structural features. Position-specific iterative BLAST showed that they had strong ancestral homology to two related families of lipid-binding proteins, namely, the bactericidal permeability-increasing (BPI) proteins and the odorant-binding protein. A three-dimensional model of Der f 7 made with the Phyre and SWISS-MODEL homology-modeling servers showed a close match with the human BPI coordinates used for its construction. The binding of the monoclonal antibody HD12 known to block IgE binding could be blocked by the linear sequence (46GILDF50) with a critical role for L48 or F50. These hydrophobic residues were located on a surface loop of the model. The properties of Der f 7 that can be deduced from the model provide avenues for further characterizing these allergens, their IgE binding structures and biological properties that can enhance allergenicity. Keywords: Der f 7; Der p 7; epitope; modeling structure; BPI protein; odorant-binding proteinThe house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae are among the major causative agents of allergic diseases, including asthma, rhinitis and atopic dermatitis. Characterizing the allergens from both mite species is important for developing better prognostic tests and improving the treatment and understanding the pathophysiological mechanisms of these prevalent human disorders.As analyzed for D. pteronyssinus, the most important house dust mite allergens are the group 1 cysteine protease and the group 2 MLdomain lipid-binding allergens. 1 Both Der p 1 and Der p 2 react with 50-65% of the anti-D. pteronyssinus IgE antibodies. 2 The Der p 4 amylase, and the Der p 5 and Der p 7 allergens of unknown function are the next most important allergens with each binding IgE in about 50% of allergic subjects. When present each binds to more than 10% of the total mite-specific IgE antibody and collectively they account for 30% of the total anti-mite IgE antibody of all HDM allergic subjects. 1,2 Der p 21, which is a homolog of Der p 5, also binds at a similar level. 3 From a quantitative perspective, most of the other allergens have low IgE binding, although the high-molecular-weight allergens, constituted by the group 11 paramyosin, the group 14 large lipid transfer protein, and group 15 and 17 chitinase-like allergens, need quantitative analysis. 1,2 The quantitative importance of the IgE binding to the group 1, 2, 4, 5 and 7 allergens is consistent with the results of studies using recombinant allergens to absorb out IgE binding to twodimensional immunoblots of mite extract. 4 Structural and functional studies of the group 1 and 2 allergens are advanced and the group 4 allergens are typical a-amylases. More information is required for the Der p 5 and the Der p 7 mite allergens. There has been recent progress on the group 5 allergens. ...

Molecular Insights of p47phox Phosphorylation Dynamics in the Regulation of NADPH Oxidase Activation and Superoxide Production

“…the N-terminal PX domain (residues 1–141, PDB: 1KQ6); the p47 phox PRR domain (residues 359–390, PDB: 1K4U) (19); and the super-SH3 domain (sSH3) (residues 159–340, the 1NG2 crystallized structure) (14), which was kindly provided by Dr. Franca Fraternali, King's College London, UK. The missing linking segments (142-MKDGKSTATDITGPII-156 and 340-PGPQSPGSPLEEERQTQRSK-360) were generated using the web-based homology protein modeling server Phyre2 as described previously (20–22). Briefly, the short residue sequences were uploaded to the server, and underwent template identification and structure refinement.…”

Hierarchy and molecular properties of house dust mite allergens

“…49 They have elongated structures with antiparallel beta-sheets wrapped around a helix to create a lipid-binding domain. Der p 7 and Der f 7 seem not to bind LPS but weakly bind the fungal lipopeptide polymyxin B.…”

Crystal Structure of Der f 7, a Dust Mite Allergen from Dermatophagoides farinae

“…An isoform of Der f 7 has been cloned, expressed and the secondary structure characterized [8], but the detailed three-dimensional structure of Der f 7 is not available. A three-dimensional model of Der f 7 was generated using homology modeling, based on the crystal structure of Der p 7 and used for mAb binding studies [9]. Immunodot blot experiments using overlapping peptides derived from Der f 7 identified Leu48 and Phe50 as the residues that were important for its interaction with HD12, a Der f 7-specific mAb that blocked IgE binding [6], [9].…”

“…A three-dimensional model of Der f 7 was generated using homology modeling, based on the crystal structure of Der p 7 and used for mAb binding studies [9]. Immunodot blot experiments using overlapping peptides derived from Der f 7 identified Leu48 and Phe50 as the residues that were important for its interaction with HD12, a Der f 7-specific mAb that blocked IgE binding [6], [9]. The corresponding residues on Der p 7, Ile48 and Leu50, do not react with mAb HD12, suggesting that residues Leu48 and Phe50 are unique epitopes in Der f 7 [9].…”