title: High-molecular-weight allergens of the house dust mite: an apolipophorin-like cDNA has sequence identity with the major M-177 allergen and the IgE-binding peptide fragments Mag1 and Mag3.
abstract: BACKGROUND
  A 349-residue recombinant polypeptide of Dermatophagoides farinae, Mag 3, has been shown to represent part of a larger 177-kD (M-177) allergen with very high IgE-binding activity.
  
  
  METHODS
  Cloning and sequencing of cDNA from the house dust mites Dermatophagoides pteronyssinus and Euroglyphus maynei was used to characterise the polypeptide containing the Mag 3 sequence.
  
  
  RESULTS
  cDNA clones containing the complete sequence of the E. maynei homologue of the M-177 allergen were isolated and analysed. The translation contained not only an amino acid sequence with 90% identity to the 349-residue Mag-3 fragment but also a further sequence with 90% identity to another IgE-binding recombinant D. farinae polypeptide designated Mag 1. The complete sequence encoded a mature polypeptide of 1,650 residues and a molecular mass of 189.5 kD. cDNA clones from D. pteronyssinus also encoded sequences equivalent to the Mag 1 and 3 polypeptides. The M-177 sequence showed strong similarity to the lipid transport apolipophorins found in insect lipophorins.
  
  
  CONCLUSIONS
  cDNA sequence data show that the D. pteronyssinus and E. maynei homologues of the M-177 high-molecular-weight D. farinae allergen contain sequences equivalent to both the Mag 1 and Mag 3 recombinant IgE-binding fragments. The N-terminal sequence of the full-length 1,650 amino-acid allergen showed strong similarity to the insect apolipophorins which are poorly soluble in aqueous extracts and exist in the lipid transport particles in haemolymph. It is proposed that presentation in lipid particles could be a factor which enhances the immunogenicity of this group of allergens.
authors.affiliation: TVW Telethon Institute for Child Health Research, West Perth, Western Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Epton
authors.forename: R J
authors.initials: RJ
authors.lastname: Dilworth
authors.forename: W
authors.initials: W
authors.lastname: Smith
authors.forename: B J
authors.initials: BJ
authors.lastname: Hart
authors.forename: W R
authors.initials: WR
authors.lastname: Thomas
mesh_terms: D000485:Allergens / Q000235:genetics / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D039741:Antigens, Dermatophagoides; D001053:Apolipoproteins / Q000235:genetics / Q000276:immunology*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000032:analysis; D004330:Drosophila; D004391:Dust; D015723:Gene Library; D006023:Glycoproteins / Q000235:genetics / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology*; D018402:Manduca; D008925:Mites / Q000276:immunology*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D000485:Allergens; D039741:Antigens, Dermatophagoides; D001053:Apolipoproteins; D018076:DNA, Complementary; D004391:Dust; D006023:Glycoproteins; D012333:RNA, Messenger; D007073:Immunoglobulin E