3bk9 | pdb_00003bk9

H55A mutant of tryptophan 2,3-dioxygenase from Xanthomonas campestris

spinqualitylabelsall models 3bk9, resolution 2.15Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3bk9 is a 8 chain structure with sequence from Xanthomonas campestris pv. campestris. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.15Å Ligands: HEM, TRP Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function T23O_XANCP Catalyzes the oxidative cleavage of the L-tryptophan (L-Trp) pyrrole ring.[HAMAP-Rule:MF_01972] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Tryptophan 2,3-dioxygenase (TDO) from Xanthomonas campestris is a highly specific heme-containing enzyme from a small family of homologous enzymes, which includes indoleamine 2,3-dioxygenase (IDO). The structure of wild type (WT TDO) in the catalytically active, ferrous (Fe (2+)) form and in complex with its substrate l-tryptophan ( l-Trp) was recently reported [Forouhar et al. (2007) Proc. Natl. Acad. Sci. U.S.A. 104, 473-478] and revealed that histidine 55 hydrogen bonds to l-Trp, precisely positioning it in the active site and implicating it as a possible active site base. In this study the substitution of the active site residue histidine 55 by alanine and serine (H55A and H55S) provides insight into the molecular mechanism used by the enzyme to control substrate binding. We report the crystal structure of the H55A and H55S mutant forms at 2.15 and 1.90 A resolution, respectively, in binary complexes with l-Trp. These structural data, in conjunction with potentiometric and kinetic studies on both mutants, reveal that histidine 55 is not essential for turnover but greatly disfavors the mechanistically unproductive binding of l-Trp to the oxidized enzyme allowing control of catalysis. This is demonstrated by the difference in the K d values for l-Trp binding to the two oxidation states of wild-type TDO (3.8 mM oxidized, 4.1 microM reduced), H55A TDO (11.8 microM oxidized, 3.7 microM reduced), and H55S TDO (18.4 microM oxidized, 5.3 microM reduced). Histidine 55 of tryptophan 2,3-dioxygenase is not an active site base but regulates catalysis by controlling substrate binding.,Thackray SJ, Bruckmann C, Anderson JL, Campbell LP, Xiao R, Zhao L, Mowat CG, Forouhar F, Tong L, Chapman SK Biochemistry. 2008 Oct 7;47(40):10677-84. Epub 2008 Sep 11. PMID:18783250 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Dioxygenase 3D structures

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