Studies

Since over 40 enzymes will be investigated for their mRNA abundance, processing, and degradation kinetics, the less tedious and more accurate Next Generation Sequencing of the entire mRNA repertoire of the cell is employed. To optimise the proportion of useful sequence, while including RNA fragments that are products of of degradation, rRNA is depleted using the eukaryotic Ribominus kit (Ambion). Two biological replicates are treated with Sinefungin and Actinomycin D to inhibit RNA processing and ...

The enzyme Trypanothione Synthetase (TryS) is a complex enzyme that catalyses the two step reaction that forms trypanothione from 2 molecules of GSH and 1 molecule of Spd and the use of ATP

Flux will be measured using the metabolomics platforms based on absolute quantification method (isotope ratio based MS technique) by LC-MS, using heavy-isotope labelled precursors of the metabolites of interest. For example, 15N labelled cysteine, glycine and glutamate will be used to determine rates of synthesis of glutathione. 15N-labelled methionine to measure S-adenosyl methionine (and its decarboxylated form, as well as methionine cycle intermediates). 15N labelled arginine is used as precursor ...

In addition to the highly targeted quantification of metabolites already known to play major roles in oxidative stress, to provide data directly compatible with current models, we will also take an untargeted metabolomics approach. This will enable us to identify other areas of the metabolome influenced by, or influencing, oxidative stress and will allow us to compare changes in each of the stress-inducing stimuli. We have recently pioneered untargeted metabolite profiling of T. brucei using ...

We have already demonstrated that the key metabolites of polyamine biosynthesis (arginine, ornithine, putrescine and spermidine) can be identified using HILIC chromatography coupled to the Orbitrap mass spectrometer, as can glycine, glutamate and cysteine used in glutathione biosynthesis, glutathionyl spermidine and trypanothione itself. Furthermore the key metabolites of the methionine cycle (methionine, S-adenosyl methionine, decarboxylated S-adenosyl methionine, methylthioadenosine) can all ...

Parasites will be harvested at different growth phases and the total amount of the proteins will be followed by western blot. The absolut concentration will be obtained by comparison with a know amount of the recombinant untagged protein. The thiol redox state of the proteins will be followed by modification of the free cys with methoxy-ethyl-maleinimide poly(ethylenglycol) (Meo-PEG-mal).

The enzymes involved in the trypanothione metabolism will be studied in a uniform assay medium that mimics the intracellular milieu of the parasite.

Key enzymes of critical points in the pathways will be targeted for disruption by the generation of RNAi cell lines and lines which drive tetracycline-regulatable ectopic over expression of either wild type enzyme or, if appropriate, dominant-negative or mis-targeted mutants of these. In all cases perturbed lines will be analysed with respect to the mRNA, protein or enzymatic activities of other components of the subsystem, this being directed iteratively by the predictions from systems modelling. ...

The output of the initial model of redox metabolism will be compared to experimental flux and metabolite data. Deviations between model and experiment will be prioritized together with WP2. We will apply Metabolic Control Analysis (Fell 1992 PMID: 1530563) to diagnose which enzymes control the deviating metabolite concentrations and/or rates. When the agreement between model and experiment is sufficient we will first link it to the existing model of trypanosome glycolysis and repeat the same ...

Our current gene-expression model (Haanstra et al. 2008 PMID: 19008351) will be parameterized for the different genes of interest. The framework of this gene expression model has been used to include mRNA half life data into the model of glycolysis For the enzymes of redox metabolism we will use newly measured rates of transcription, RNA precursor degradation, mRNA degradation, concentrations of mature mRNAs and proteins, enzyme turnover, Vmax values and metabolic fluxes (WP3&5). Regulation ...

We are in the process of construct an ODE model of the trypanothione pathway. As input we will use newly determined and existing kinetic data and measured metabolite concentrations at the boundaries (from WP3&6). Recently the glycolysis model was extended with the pentose phosphate pathway. This pathway will yield the NAPDH that maintains trypanothione in a reduced state. For some complex enzymes (i.e trypanothione synthase) we are intensively discussing the kinetic data obtained on the ...