title: Identification of two binding proteins for halogenated aromatic hydrocarbons in the hard-shell clam, Mercenaria mercenaria.
abstract: Earlier studies have reported an unusually high incidence of gonadal tumors in marine bivalves in areas of potentially high exposure to herbicides including 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophe-noxyacetic acid. Some herbicides can be contaminated by halogenated aromatic compounds including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Most of the effects of planar halogenated aromatic compounds, including carcinogenic effects in vertebrates, appear to be mediated through binding to the aryl hydrocarbon receptor. The current study investigated whether halogenated aromatic hydrocarbon-binding proteins are present in the marine bivalve, Mercenaria mercenaria. We used the TCDD photoaffinity analog 2-azido-3-[125I]-iodo-7, 8-dibromodibenzo-p-dioxin to detect the presence of two proteins (28 and 39 kDa) in cytosols prepared from M. mercenaria that specifically bound this ligand. Expression of these proteins is tissue-dependent with the highest concentrations being observed in gill and gonadal tissue. Gonadal tissue also exhibited gender-specific expression with female clams exhibiting higher levels of the 39-kDa protein. Gender-and tissue-specific expression are consistent with the hypothesis that these proteins might be involved in the carcinogenic response observed in clams exposed to herbicides.
authors.affiliation: Department of Cell Biology, Duke University, Durham, North Carolina 27710, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Brown
authors.forename: R J
authors.initials: RJ
authors.lastname: Van Beneden
authors.forename: G C
authors.initials: GC
authors.lastname: Clark
mesh_terms: D000345:Affinity Labels; D000595:Amino Acid Sequence; D000818:Animals; D049872:Bivalvia / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D005260:Female; D006066:Gonads / Q000187:drug effects / Q000378:metabolism; D006846:Hydrocarbons, Halogenated / Q000378:metabolism* / Q000633:toxicity; D008024:Ligands; D008297:Male; D008969:Molecular Sequence Data; D008970:Molecular Weight; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism / Q000633:toxicity; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity
chemical_list: D000345:Affinity Labels; D002352:Carrier Proteins; D006846:Hydrocarbons, Halogenated; D008024:Ligands; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D014874:Water Pollutants, Chemical