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Crystal structure and solution characterization of the thioredoxin-2 from Plasmodium falciparum, a constituent of an essential parasitic protein export complex.

ABSTRACT: Survival of the malaria parasite Plasmodium falciparum when it infects red blood cells depends upon its ability to export hundreds of its proteins beyond an encasing vacuole. Protein export is mediated by a parasite-derived protein complex, the Plasmodium translocon of exported proteins (PTEX), and requires unfolding of the different cargos prior to their translocation across the vacuolar membrane. Unfolding is performed by the AAA+protein unfoldase HSP101/ClpB2 and the thioredoxin-2 enzyme (TRX2). Protein trafficking is dramatically impaired in parasites with defective HSP101 or lacking TRX2. These two PTEX subunits drive export and are targets for the design of a novel class of antimalarials: protein export inhibitors. To rationalize inhibitor design, we solved the crystal structure of Pfal-TRX2 at 2.2-Å resolution. Within the asymmetric unit, the three different copies of this protein disulfide reductase sample its two redox catalytic states. Size exclusion chromatography and small-angle X-ray scattering (SAXS) analyses demonstrate that Pfal-TRX2 is monomeric in solution. A non-conserved N-terminal extension precedes the canonical thioredoxin-fold; although it is not observed in our structure, our solution analysis suggests it is flexible in contrast to Plasmodium thioredoxin-1. This represents a first step towards the reconstitution of the entire PTEX for mechanistic and structural studies.

SUBMITTER: Peng M

PROVIDER: S-EPMC5023060 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature

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Crystal structure and solution characterization of the thioredoxin-2 from Plasmodium falciparum, a constituent of an essential parasitic protein export complex.

Peng Mindy M Cascio Duilio D Egea Pascal F PF

Biochemical and biophysical research communications 20141202 1

Survival of the malaria parasite Plasmodium falciparum when it infects red blood cells depends upon its ability to export hundreds of its proteins beyond an encasing vacuole. Protein export is mediated by a parasite-derived protein complex, the Plasmodium translocon of exported proteins (PTEX), and requires unfolding of the different cargos prior to their translocation across the vacuolar membrane. Unfolding is performed by the AAA+protein unfoldase HSP101/ClpB2 and the thioredoxin-2 enzyme (TRX ...[more]

PMID: 25475729

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Project description:The malarial parasite Plasmodium falciparum possesses a functional thioredoxin and glutathione system comprising the dithiol-containing redox proteins thioredoxin (Trx) and glutaredoxin (Grx), as well as plasmoredoxin (Plrx), which is exclusively found in Plasmodium species. All three proteins belong to the thioredoxin superfamily and share a conserved Cys-X-X-Cys motif at the active site. Only a few of their target proteins, which are likely to be involved in redox reactions, are currently known. The aim of the present study was to extend our knowledge of the Trx-, Grx-, and Plrx-interactome in Plasmodium. Based on the reaction mechanism, we generated active site mutants of Trx and Grx lacking the resolving cysteine residue. These mutants were bound to affinity columns to trap target proteins from P. falciparum cell extracts after formation of intermolecular disulfide bonds. Covalently linked proteins were eluted with dithiothreitol and analyzed by mass spectrometry. For Trx and Grx, we were able to isolate 17 putatively redox-regulated proteins each. Furthermore, the approach was successfully established for Plrx, leading to the identification of 21 potential target proteins. In addition to confirming known interaction partners, we captured potential target proteins involved in various processes including protein biosynthesis, energy metabolism, and signal transduction. The identification of three enzymes involved in S-adenosylmethionine (SAM) metabolism furthermore suggests that redox control is required to balance the metabolic fluxes of SAM between methyl-group transfer reactions and polyamine synthesis. To substantiate our data, the binding of the redoxins to S-adenosyl-L-homocysteine hydrolase and ornithine aminotransferase (OAT) were verified using BIAcore surface plasmon resonance. In enzymatic assays, Trx was furthermore shown to enhance the activity of OAT. Our approach led to the discovery of several putatively redox-regulated proteins, thereby contributing to our understanding of the redox interactome in malarial parasites.

Dataset Information

Crystal structure and solution characterization of the thioredoxin-2 from Plasmodium falciparum, a constituent of an essential parasitic protein export complex.

Publications

Crystal structure and solution characterization of the thioredoxin-2 from Plasmodium falciparum, a constituent of an essential parasitic protein export complex.

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