title: Molecular basis for catalysis and substrate-mediated cellular stabilization of human tryptophan 2,3-dioxygenase.
abstract: Tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) play a central role in tryptophan metabolism and are involved in many cellular and disease processes. Here we report the crystal structure of human TDO (hTDO) in a ternary complex with the substrates L-Trp and O2and in a binary complex with the product N-formylkynurenine (NFK), defining for the first time the binding modes of both substrates and the product of this enzyme. The structure indicates that the dioxygenation reaction is initiated by a direct attack of O2on the C2atom of the L-Trp indole ring. The structure also reveals an exo binding site for L-Trp, located ~42 Å from the active site and formed by residues conserved among tryptophan-auxotrophic TDOs. Biochemical and cellular studies indicate that Trp binding at this exo site does not affect enzyme catalysis but instead it retards the degradation of hTDO through the ubiquitin-dependent proteasomal pathway. This exo site may therefore provide a novel L-Trp-mediated regulation mechanism for cellular degradation of hTDO, which may have important implications in human diseases.
authors.affiliation: Department of Physiology and Biophysics Albert Einstein College of Medicine Bronx, NY 10461, USA.
authors.forename: Ariel
authors.initials: A
authors.lastname: Lewis-Ballester
authors.affiliation: Department of Biological Sciences Northeast Structural Genomics Consortium Columbia University New York, NY 10027, USA.
authors.forename: Farhad
authors.initials: F
authors.lastname: Forouhar
authors.affiliation: Departments of Cellular and Molecular Pharmacology, Pharmaceutical Chemistry, and Bioengineering and Therapeutic Sciences, The Liver Center, University of California at San Francisco San Francisco, CA 94158, USA.
authors.forename: Sung-Mi
authors.initials: SM
authors.lastname: Kim
authors.affiliation: Department of Biological Sciences Northeast Structural Genomics Consortium Columbia University New York, NY 10027, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Lew
authors.affiliation: Departments of Cellular and Molecular Pharmacology, Pharmaceutical Chemistry, and Bioengineering and Therapeutic Sciences, The Liver Center, University of California at San Francisco San Francisco, CA 94158, USA.
authors.forename: YongQiang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Physiology and Biophysics Albert Einstein College of Medicine Bronx, NY 10461, USA.
authors.forename: Shay
authors.initials: S
authors.lastname: Karkashon
authors.affiliation: Department of Biological Sciences Northeast Structural Genomics Consortium Columbia University New York, NY 10027, USA.
authors.forename: Jayaraman
authors.initials: J
authors.lastname: Seetharaman
authors.affiliation: Department of Physiology and Biophysics Albert Einstein College of Medicine Bronx, NY 10461, USA.
authors.forename: Dipanwita
authors.initials: D
authors.lastname: Batabyal
authors.affiliation: Department of Physiology and Biophysics Albert Einstein College of Medicine Bronx, NY 10461, USA.
authors.forename: Bing-Yu
authors.initials: BY
authors.lastname: Chiang
authors.affiliation: Department of Biological Sciences Northeast Structural Genomics Consortium Columbia University New York, NY 10027, USA.
authors.forename: Munif
authors.initials: M
authors.lastname: Hussain
authors.affiliation: Departments of Cellular and Molecular Pharmacology, Pharmaceutical Chemistry, and Bioengineering and Therapeutic Sciences, The Liver Center, University of California at San Francisco San Francisco, CA 94158, USA.
authors.forename: Maria Almira
authors.initials: MA
authors.lastname: Correia
authors.affiliation: Department of Physiology and Biophysics Albert Einstein College of Medicine Bronx, NY 10461, USA.
authors.forename: Syun-Ru
authors.initials: SR
authors.lastname: Yeh
authors.affiliation: Department of Biological Sciences Northeast Structural Genomics Consortium Columbia University New York, NY 10027, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Tong
mesh_terms: D002384:Catalysis; D018360:Crystallography, X-Ray; D006801:Humans; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000737:chemistry*; D007737:Kynurenine / Q000031:analogs & derivatives / Q000096:biosynthesis; D010100:Oxygen / Q000737:chemistry*; D011485:Protein Binding / Q000502:physiology; D017433:Protein Structure, Secondary; D014364:Tryptophan / Q000737:chemistry*; D014366:Tryptophan Oxygenase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; C007772:N'-formylkynurenine; D007737:Kynurenine; D014364:Tryptophan; D014366:Tryptophan Oxygenase; D010100:Oxygen