title: The novel structure of the cockroach allergen Bla g 1 has implications for allergenicity and exposure assessment.
abstract: BACKGROUND
  Sensitization to cockroach allergens is a major risk factor for asthma. The cockroach allergen Bla g 1 has multiple repeats of approximately 100 amino acids, but the fold of the protein and its biological function are unknown.
  
  
  OBJECTIVE
  We sought to determine the structure of Bla g 1, investigate the implications for allergic disease, and standardize cockroach exposure assays.
  
  
  METHODS
  nBla g 1 and recombinant constructs were compared by using ELISA with specific murine IgG and human IgE. The structure of Bla g 1 was determined by x-ray crystallography. Mass spectrometry and nuclear magnetic resonance spectroscopy were used to examine the ligand-binding properties of the allergen.
  
  
  RESULTS
  The structure of an rBla g 1 construct with comparable IgE and IgG reactivity to the natural allergen was solved by x-ray crystallography. The Bla g 1 repeat forms a novel fold with 6 helices. Two repeats encapsulate a large and nearly spherical hydrophobic cavity, defining the basic structural unit. Lipids in the cavity varied depending on the allergen origin. Palmitic, oleic, and stearic acids were associated with nBla g 1 from cockroach frass. One unit of Bla g 1 was equivalent to 104 ng of allergen.
  
  
  CONCLUSIONS
  Bla g 1 has a novel fold with a capacity to bind various lipids, which suggests a digestive function associated with nonspecific transport of lipid molecules in cockroaches. Defining the basic structural unit of Bla g 1 facilitates the standardization of assays in absolute units for the assessment of environmental allergen exposure.
authors.affiliation: Laboratory of Structural Biology, National Institute of Environmental Health Sciences, Research Triangle Park, NC. Electronic address: Mueller3@niehs.nih.gov.
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Mueller
authors.forename: Lars C
authors.initials: LC
authors.lastname: Pedersen
authors.forename: Fred B
authors.initials: FB
authors.lastname: Lih
authors.forename: Jill
authors.initials: J
authors.lastname: Glesner
authors.forename: Andrea F
authors.initials: AF
authors.lastname: Moon
authors.forename: Martin D
authors.initials: MD
authors.lastname: Chapman
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Tomer
authors.forename: Robert E
authors.initials: RE
authors.lastname: London
authors.forename: Anna
authors.initials: A
authors.lastname: Pomés
mesh_terms: D000485:Allergens / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001249:Asthma / Q000175:diagnosis* / Q000276:immunology*; D003058:Cockroaches; D018360:Crystallography, X-Ray; D004063:Digestion / Q000235:genetics; D004781:Environmental Exposure / Q000009:adverse effects; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology / Q000378:metabolism*; D008055:Lipids / Q000276:immunology; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D016415:Sequence Alignment; D019076:Transgenes / Q000235:genetics
chemical_list: D000485:Allergens; D008055:Lipids; C105482:allergen Bla g 1; D007073:Immunoglobulin E
keywords: Allergen; Bla g 1; GFP; GST; Glutathione-S-transferase; Green fluorescent protein; MS; Mass spectrometry; NMR; NSP; Nitrile-specifier protein; Nuclear magnetic resonance spectroscopy; PC; PE; PG; PI; Phosphatidylcholine; Phosphatidylethanolamine; Phosphatidylglycerol; Phosphatidylinositol; Recombinant Bla g 1 expressed in Escherichia coli; Recombinant Bla g 1 expressed in Pichia pastoris; Recombinant Bla g 1 with an N-terminal GFP; TEV; TLR; Tobacco etch virus; Toll-like receptor; asthma; cockroach; exposure assessment; ligand-binding proteins; rBla g 1–EC; rBla g 1–GFP; rBla g 1–PP; structure
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