title: Structural stability and heme binding potential of the truncated human dual oxidase 2 (DUOX2) peroxidase domain.
abstract: The essential role of human dual oxidase 2 (hDUOX2) in thyroid hormone biosynthesis defines this member of the NOX/DUOX family, whose absence due to mutation has been directly related to disease, specifically hypothyroidism. Both human DUOX isoforms, hDUOX1 and hDUOX2, are expressed in thyroid tissue; however, hDUOX1 cannot compensate for inactivation of hDUOX2, suggesting that each enzyme is differentially regulated and/or functions in a unique manner. In efforts to uncover relevant structural and functional differences we have expressed and purified the peroxidase domain of hDUOX2(1-599) for direct comparison with the previously studied hDUOX1(1-593). As was shown for hDUOX1, the truncated hDUOX2 domain purifies without a bound heme co-factor and displays no peroxidase activity. However, hDUOX2(1-599) displays greater stability than hDUOX1(1-593). Surprisingly, upon titration with heme, both isoforms bind heme with a low micromolar affinity, demonstrating that they retain a heme binding site. A conformational difference in the full-length protein and/or a protein-protein interaction may be required to increase the heme binding affinity.
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco, United States.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Meitzler
authors.forename: Paul R
authors.initials: PR
authors.lastname: Ortiz de Montellano
mesh_terms: D000595:Amino Acid Sequence; D000074623:Dual Oxidases; D004795:Enzyme Stability; D006418:Heme / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019255:NADPH Oxidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012995:Solubility
chemical_list: D010446:Peptide Fragments; D011994:Recombinant Proteins; D006418:Heme; D000074623:Dual Oxidases; D019255:NADPH Oxidases; C431513:DUOX1 protein, human; C431515:DUOX2 protein, human