title: Echinococcus granulosus antigen B hydrophobic ligand binding properties.
abstract: Antigen B (AgB), an immunodominant component of the cestode parasite Echinococcus granulosus, presents homology to and shares apparent structural similarities with helix-rich hydrophobic ligand binding proteins (HLBPs) from other cestodes. In order to investigate the fatty acid binding properties of AgB, two of its subunit components (rAgB8/1 and rAgB8/2) were expressed in Escherichia coli and purified, and the native antigen was purified from the hydatid cyst fluid by affinity chromatography using a monoclonal antibody raised against rAgB8/1. The interaction of the purified native and recombinant proteins with the fluorescent ligands DAUDA, ANS, DACA and 16-AP was investigated. The palmitic acid derived fluorescent ligand, 16-AP, showed the greatest enhancement in fluorescence when bound to native AgB or to its recombinant subunits, and the dissociation constants for 16-AP binding were determined. Surprisingly, in contrast to HLBPs from other cestodes, interactions with other fatty acids, including palmitic acid, caused an increase in fluorescence instead of competing with 16-AP. Our results suggest that AgB might have evolved different functions in the binding of hydrophobic compounds, dependent on cestode environment.
authors.affiliation: Centro de Biotecnologia and Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Caixa Postal 15005, Porto Alegre, RS, 91501-970, Brazil.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Chemale
authors.forename: Henrique B
authors.initials: HB
authors.lastname: Ferreira
authors.forename: John
authors.initials: J
authors.lastname: Barrett
authors.forename: Peter M
authors.initials: PM
authors.lastname: Brophy
authors.forename: Arnaldo
authors.initials: A
authors.lastname: Zaha
mesh_terms: D000818:Animals; D000909:Antibodies, Helminth / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D001665:Binding Sites; D002589:Cestoda / Q000737:chemistry / Q000378:metabolism; D002846:Chromatography, Affinity; D020420:Cyst Fluid / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D015801:Helminth Proteins / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008024:Ligands; D008074:Lipoproteins / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D000909:Antibodies, Helminth; D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D005227:Fatty Acids; D015801:Helminth Proteins; D008024:Ligands; D008074:Lipoproteins; C484346:RagB protein, bacteria; D011993:Recombinant Fusion Proteins; C089273:antigen B, Echinococcus