Abstract
Blastomyces adhesin-1 (BAD-1) is a 120-kD surface protein on B. dermatitidis yeast. We show here that BAD-1 contains 41 tandem repeats and that deleting even half of them impairs fungal pathogenicity. According to NMR, the repeats form tightly folded 17-amino acid loops constrained by a disulfide bond linking conserved cysteines. Each loop contains a highly conserved WxxWxxW motif found in thrombospondin-1 (TSP-1) type 1 heparin-binding repeats. BAD-1 binds heparin specifically and saturably, and is competitively inhibited by soluble heparin, but not related glycosaminoglycans. According to SPR analysis, the affinity of BAD-1 for heparin is 33 nM±14 nM. Putative heparin-binding motifs are found both at the N-terminus and within each tandem repeat loop. Like TSP-1, BAD-1 blocks activation of T cells in a manner requiring the heparan sulfate-modified surface molecule CD47, and impairs effector functions. The tandem repeats of BAD-1 thus confer pathogenicity, harbor motifs that bind heparin, and suppress T-cell activation via a CD47-dependent mechanism, mimicking mammalian TSP-1.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Animals
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Antigens, Fungal / chemistry
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Antigens, Fungal / genetics
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Antigens, Fungal / metabolism*
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Antigens, Surface / chemistry
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Antigens, Surface / genetics
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Antigens, Surface / metabolism*
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Blastomyces / chemistry
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Blastomyces / immunology*
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Blastomyces / metabolism
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Blastomyces / pathogenicity
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Blastomycosis / immunology
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Blastomycosis / metabolism
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Blastomycosis / microbiology
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CD47 Antigen / chemistry
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CD47 Antigen / genetics
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CD47 Antigen / metabolism
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Cells, Cultured
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Fungal Proteins / chemistry
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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Heparin / metabolism*
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Humans
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Jurkat Cells
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Lymphocyte Activation*
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Male
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Mice, Inbred BALB C
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Mice, Transgenic
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Mutant Proteins / chemistry
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Mutant Proteins / metabolism
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Peptide Fragments / chemistry
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Peptide Fragments / genetics
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Peptide Fragments / metabolism
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Recombinant Proteins / chemistry
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Recombinant Proteins / metabolism
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T-Lymphocytes / cytology
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T-Lymphocytes / immunology*
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T-Lymphocytes / metabolism
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Tandem Repeat Sequences
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Thrombospondin 1 / chemistry
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Thrombospondin 1 / metabolism
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Virulence
Substances
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Antigens, Fungal
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Antigens, Surface
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CD47 Antigen
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Fungal Proteins
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Mutant Proteins
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Peptide Fragments
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Recombinant Proteins
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Thrombospondin 1
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Heparin