title: Interaction of Azole-Based Environmental Pollutants with the Coelomic Hemoglobin from Amphitrite ornata: A Molecular Basis for Toxicity.
abstract: The toxicities of azole pollutants that have widespread agricultural and industrial uses are either poorly understood or unknown, particularly with respect to how infaunal organisms are impacted by this class of persistent organic pollutant. To identify a molecular basis by which azole compounds may have unforeseen toxicity on marine annelids, we examine here their impact on the multifunctional dehaloperoxidase (DHP) hemoglobin from the terebellid polychaete Amphitrite ornata. Ultraviolet-visible and resonance Raman spectroscopic studies showed an increase in the six-coordinate low-spin heme population in DHP isoenzyme B upon binding of imidazole, benzotriazole, and benzimidazole (Kdvalues of 52, 82, and 110 μM, respectively), suggestive of their direct binding to the heme-Fe. Accordingly, atomic-resolution X-ray crystal structures, supported by computational studies, of the DHP B complexes of benzotriazole (1.14 Å), benzimidazole (1.08 Å), imidazole (1.08 Å), and indazole (1.12 Å) revealed two ligand binding motifs, one with direct ligand binding to the heme-Fe, and another in which the ligand binds in the hydrophobic distal pocket without coordinating the heme-Fe. Taken together, the results demonstrate a new mechanism by which azole pollutants can potentially disrupt hemoglobin function, thereby improving our understanding of their impact on infaunal organisms in marine and aquatic environments.
authors.affiliation: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States.
authors.forename: Nikolette L
authors.initials: NL
authors.lastname: McCombs
authors.affiliation: School of Biological Sciences, University of Essex , Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K.
authors.forename: Tadeo
authors.initials: T
authors.lastname: Moreno-Chicano
authors.affiliation: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States.
authors.forename: Leiah M
authors.initials: LM
authors.lastname: Carey
authors.affiliation: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States.
authors.forename: Stefan
authors.initials: S
authors.lastname: Franzen
authors.affiliation: School of Biological Sciences, University of Essex , Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hough
authors.affiliation: Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695-8204, United States.
authors.forename: Reza A
authors.identifier: 0000-0002-6450-9311
authors.initials: RA
authors.lastname: Ghiladi
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001562:Benzimidazoles / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D020134:Catalytic Domain; D019295:Computational Biology; D004785:Environmental Pollutants / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D005659:Fungicides, Industrial / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D006454:Hemoglobins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D007191:Indazoles / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D010544:Peroxidases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D010575:Pesticides / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D011077:Polychaeta / Q000201:enzymology*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D014230:Triazoles / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity
chemical_list: D001562:Benzimidazoles; D004785:Environmental Pollutants; D004791:Enzyme Inhibitors; D005659:Fungicides, Industrial; D006454:Hemoglobins; D007093:Imidazoles; D007191:Indazoles; D007527:Isoenzymes; D008024:Ligands; D010575:Pesticides; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D014230:Triazoles; C029899:imidazole; C012771:benzotriazole; C031000:benzimidazole; C098661:DHP I dehaloperoxidase; D010544:Peroxidases