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Molecular dynamics reveal binding mode of glutathionylspermidine by trypanothione synthetase.

ABSTRACT: The trypanothione synthetase (TryS) catalyses the two-step biosynthesis of trypanothione from spermidine and glutathione and is an attractive new drug target for the development of trypanocidal and antileishmanial drugs, especially since the structural information of TryS from Leishmania major has become available. Unfortunately, the TryS structure was solved without any of the substrates and lacks loop regions that are mechanistically important. This contribution describes docking and molecular dynamics simulations that led to further insights into trypanothione biosynthesis and, in particular, explains the binding modes of substrates for the second catalytic step. The structural model essentially confirm previously proposed binding sites for glutathione, ATP and two Mg(2+) ions, which appear identical for both catalytic steps. The analysis of an unsolved loop region near the proposed spermidine binding site revealed a new pocket that was demonstrated to bind glutathionylspermidine in an inverted orientation. For the second step of trypanothione synthesis glutathionylspermidine is bound in a way that preferentially allows N(1)-glutathionylation of N(8)-glutathionylspermidine, classifying N(8)-glutathionylspermidine as the favoured substrate. By inhibitor docking, the binding site for N(8)-glutathionylspermidine was characterised as druggable.

SUBMITTER: Koch O

PROVIDER: S-EPMC3581523 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Molecular dynamics reveal binding mode of glutathionylspermidine by trypanothione synthetase.

Koch Oliver O Cappel Daniel D Nocker Monika M Jäger Timo T Flohé Leopold L Sotriffer Christoph A CA Selzer Paul M PM

PloS one 20130225 2

The trypanothione synthetase (TryS) catalyses the two-step biosynthesis of trypanothione from spermidine and glutathione and is an attractive new drug target for the development of trypanocidal and antileishmanial drugs, especially since the structural information of TryS from Leishmania major has become available. Unfortunately, the TryS structure was solved without any of the substrates and lacks loop regions that are mechanistically important. This contribution describes docking and molecular ...[more]

PMID: 23451087

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Project description:BACKGROUND:The search for novel chemical entities targeting essential and parasite-specific pathways is considered a priority for neglected diseases such as trypanosomiasis and leishmaniasis. The thiol-dependent redox metabolism of trypanosomatids relies on bis-glutathionylspermidine [trypanothione, T(SH)2], a low molecular mass cosubstrate absent in the host. In pathogenic trypanosomatids, a single enzyme, trypanothione synthetase (TryS), catalyzes trypanothione biosynthesis, which is indispensable for parasite survival. Thus, TryS qualifies as an attractive drug target candidate. METHODOLOGY/PRINCIPAL FINDING:A library composed of 144 compounds from 7 different families and several singletons was screened against TryS from three major pathogen species (Trypanosoma brucei, Trypanosoma cruzi and Leishmania infantum). The screening conditions were adjusted to the TryS´ kinetic parameters and intracellular concentration of substrates corresponding to each trypanosomatid species, and/or to avoid assay interference. The screening assay yielded suitable Z' and signal to noise values (?0.85 and ~3.5, respectively), and high intra-assay reproducibility. Several novel chemical scaffolds were identified as low ?M and selective tri-tryp TryS inhibitors. Compounds displaying multi-TryS inhibition (N,N'-bis(3,4-substituted-benzyl) diamine derivatives) and an N5-substituted paullone (MOL2008) halted the proliferation of infective Trypanosoma brucei (EC50 in the nM range) and Leishmania infantum promastigotes (EC50 = 12 ?M), respectively. A bis-benzyl diamine derivative and MOL2008 depleted intracellular trypanothione in treated parasites, which confirmed the on-target activity of these compounds. CONCLUSIONS/SIGNIFICANCE:Novel molecular scaffolds with on-target mode of action were identified as hit candidates for TryS inhibition. Due to the remarkable species-specificity exhibited by tri-tryp TryS towards the compounds, future optimization and screening campaigns should aim at designing and detecting, respectively, more potent and broad-range TryS inhibitors.

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Molecular dynamics reveal binding mode of glutathionylspermidine by trypanothione synthetase.

Publications

Molecular dynamics reveal binding mode of glutathionylspermidine by trypanothione synthetase.

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