Dataset Information

Inhibition Mechanisms of Human Indoleamine 2,3 Dioxygenase 1.

ABSTRACT: Human indoleamine 2,3-dioxygenase 1 (hIDO1) and tryptophan dioxygenase (hTDO) catalyze the same dioxygenation reaction of Trp to generate N-formyl kynurenine (NFK). They share high structural similarity, especially in the active site. However, hIDO1 possesses a unique inhibitory substrate binding site (Si) that is absent in hTDO. In addition, in hIDO1, the indoleamine group of the substrate Trp is H-bonded to S167 through a bridging water, while that in hTDO is directly H-bonded to H76. Here we show that Trp binding to the Si site or the mutation of S167 to histidine in hIDO1 retards its turnover activity and that the inhibited activity can be rescued by an effector, 3-indole ethanol (IDE). Kinetic studies reveal that the inhibited activity introduced by Trp binding to the Si site is a result of retarded recombination of the ferryl moiety with Trp epoxide to form NFK and that IDE reverses the effect by preventing Trp from binding to the Si site. In contrast, the abolished activity induced by the S167H mutation is primarily a result of ?5000-fold reduction in the O2 binding rate constant, possibly due to the blockage of a ligand delivery tunnel, and that IDE binding to the Si site reverses the effect by reopening the tunnel. The data offer new insights into structure-based design of hIDO1-selective inhibitors.

SUBMITTER: Lewis-Ballester A

PROVIDER: S-EPMC6434940 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Inhibition Mechanisms of Human Indoleamine 2,3 Dioxygenase 1.

Lewis-Ballester Ariel A Karkashon Shay S Batabyal Dipanwita D Poulos Thomas L TL Yeh Syun-Ru SR

Journal of the American Chemical Society 20180627 27

Human indoleamine 2,3-dioxygenase 1 (hIDO1) and tryptophan dioxygenase (hTDO) catalyze the same dioxygenation reaction of Trp to generate N-formyl kynurenine (NFK). They share high structural similarity, especially in the active site. However, hIDO1 possesses a unique inhibitory substrate binding site (Si) that is absent in hTDO. In addition, in hIDO1, the indoleamine group of the substrate Trp is H-bonded to S167 through a bridging water, while that in hTDO is directly H-bonded to H76. Here we ...[more]

PMID: 29897749

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Project description:Infection with Chlamydia pneumoniae, a human respiratory pathogen, has been associated with various chronic diseases such as asthma, coronary heart disease and importantly atherosclerosis. Possibly because the pathogen can exist in a persistent form. TNF-a has been reported to induce chlamydial persitence in epithelial cell lines, however the mechanism of TNF-a-induced persistence has not been reported. Moreover, C. pneumoniae persistently infect human dendritic cells (DCs) and activate DCs to produce cytokines including TNF-a. Induction of chlamydial persistence by other cytokines such as IFN-g is known to be due to indoleamine 2,3-dioxygenase (IDO) activity. The present study therefore, investigated whether C. pneumoniae infection can induce IDO activity in dendritic cells, and whether the restriction of chlamydial growth in the DCs by TNF-a is IDO-dependent. Our data indicate that infection of DCs with C. pneumoniae resulted in the induction of IDO expression. Reporting on our use of anti-TNF-a antibody adalimumab and varying concentrations of TNF-a, we further demonstrate that IDO induction following infection of DCs with C. pneumoniae is TNF-a-dependent. The anti-chlamydial activity induced by TNF-a and the expression of chlamydial 16S rRNA gene, euo, groEL1, ftsk and tal genes was correlated with the induction of IDO. Addition of excess amounts of tryptophan to the DC cultures resulted in abrogation of the TNF-a-mediated chlamydial growth restriction. These findings suggest that infection of DCs by C. pneumoniae induces production of functional IDO, which subsequently causes depletion of tryptophan. This may represent a potential mechanism for DCs to restrict bacterial growth in chlamydial infections. Experiment Overall Design: Human monocyte-derived DCs from five heathy donors were infected with C. pneumoniae at multiplicity of infection of 5 for 72 h. Mock-infected (uninfected) DCs were used as a control for the infection. Total RNA from 72 h chlamydiae-infected or mock-infected DCs was isolated with RNeasy Mini Kit (Qiagen, Hilden, Germany) and DNA contamination was removed with RQ1 DNase (Promega). Total RNA from all donors was pooled and the samples were processed and analyzed at the array facility of Helmholtz center for infection biology, Braunschweig. The integrity of the RNA was verified on the Agilent Bioanalyzer system. We used the Affymetrix Gene Chip Human Genome U133 2.0 Plus. Data were processed using Affymetrix software and signal intensity measured was normalized by the Affymetrix MAS5 algorithm. Data were filtered to exclude genes at background levels (non-expressors, signal intensity at 100).

Dataset Information

Inhibition Mechanisms of Human Indoleamine 2,3 Dioxygenase 1.

Publications

Inhibition Mechanisms of Human Indoleamine 2,3 Dioxygenase 1.

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