title: The variable region of iodothyronine deiodinases directs their catalytic properties and subcellular localization.
abstract: The stereospecific removal of iodine from thyroid hormones is an essential first step for T3 action and is catalyzed by three different deiodinases: D2 and D3 remove iodine only from the outer or inner ring, respectively, whereas D1 catalyzes both pathways. We used in silico predictions from vertebrate deiodinase sequences to identify two domains: the N-terminal variable region (VR) containing the transmembrane, hinge and linker domains, and the conserved or globular region (CR). Given the high sequence and structural identity of the CR among paralogs as well as of the VR among orthologs but not paralogs, we hypothesized that both the catalytic properties and the subcellular localization rely on the VR. We used shark D2 and D3 as templates to build the chimeric enzymes D2VR/D3CR and D3VR/D2CR. Biochemical characterization revealed that D3VR/D2CR has inner-ring deiodination activity and T3 as preferred substrate, whereas D2VR/D3CR showed no deiodinating activity. Also, D2VR/D3CR and D3VR/D2CR reside in the endoplasmic reticulum and plasmatic membrane, respectively, as do their D2 and D3 wild-type counterparts. We conclude that the VR determines the subcellular localization and is critical in defining the catalytic properties and activity of thyroid hormone deiodinases.
authors.affiliation: Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico.
authors.forename: Aurora
authors.initials: A
authors.lastname: Olvera
authors.affiliation: Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico.
authors.forename: Arturo
authors.initials: A
authors.lastname: Mendoza
authors.affiliation: Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico.
authors.forename: Patricia
authors.initials: P
authors.lastname: Villalobos
authors.affiliation: Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico.
authors.forename: Lidia
authors.initials: L
authors.lastname: Mayorga-Martínez
authors.affiliation: Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico. Electronic address: aureao@unam.mx.
authors.forename: Aurea
authors.initials: A
authors.lastname: Orozco
authors.affiliation: Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico.
authors.forename: Carlos
authors.initials: C
authors.lastname: Valverde-R
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D002478:Cells, Cultured; D003001:Cloning, Molecular; D029941:Fish Proteins / Q000737:chemistry* / Q000378:metabolism; D007453:Iodide Peroxidase / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D021381:Protein Transport; D012754:Sharks; D013974:Thyroxine / Q000737:chemistry; D014284:Triiodothyronine / Q000737:chemistry; D014982:Xenopus laevis
chemical_list: D029941:Fish Proteins; D014284:Triiodothyronine; D007453:Iodide Peroxidase; D013974:Thyroxine
keywords: Deiodinase catalytic selectivity; Deiodinase subcellular localization; Shark deiodinase