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The ferredoxin‐NADP + reductase/ferredoxin electron transfer system of Plasmodium falciparum
Author(s) -
Balconi Emanuela,
Pennati Andrea,
Crobu Danila,
Pandini Vittorio,
Cerutti Raffaele,
Zanetti Giuliana,
Aliverti Alessandro
Publication year - 2009
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2009.07100.x
Subject(s) - ferredoxin , plasmodium falciparum , apicoplast , flavodoxin , oxidoreductase , reductase , ferredoxin thioredoxin reductase , ferredoxin—nadp(+) reductase , biochemistry , electron transfer , biology , semiquinone , stereochemistry , enzyme , chemistry , thioredoxin , thioredoxin reductase , photochemistry , quinone , apicomplexa , malaria , immunology
In the apicoplast of apicomplexan parasites, plastidic‐type ferredoxin and ferredoxin‐NADP + reductase (FNR) form a short electron transport chain that provides reducing power for the synthesis of isoprenoid precursors. These proteins are attractive targets for the development of novel drugs against diseases such as malaria, toxoplasmosis, and coccidiosis. We have obtained ferredoxin and FNR of both Toxoplasma gondii and Plasmodium falciparum in recombinant form, and recently we solved the crystal structure of the P. falciparum reductase. Here we report on the functional properties of the latter enzyme, which differ markedly from those of homologous FNRs. In the physiological reaction, P. falciparum FNR displays a k cat five‐fold lower than those usually determined for plastidic‐type FNRs. By rapid kinetics, we found that hydride transfer between NADPH and protein‐bound FAD is slower in the P. falciparum enzyme. The redox properties of the enzyme were determined, and showed that the FAD semiquinone species is highly destabilized. We propose that these two features, i.e. slow hydride transfer and unstable FAD semiquinone, are responsible for the poor catalytic efficiency of the P. falciparum enzyme. Another unprecedented feature of the malarial parasite FNR is its ability to yield, under oxidizing conditions, an inactive dimeric form stabilized by an intermolecular disulfide bond. Here we show that the monomer–dimer interconversion can be controlled by oxidizing and reducing agents that are possibly present within the apicoplast, such as H 2 O 2 , glutathione, and lipoate. This finding suggests that modulation of the quaternary structure of P. falciparum FNR might represent a regulatory mechanism, although this needs to be verified in vivo . Structured digital abstract• MINT‐7042675 : PfFNR (genbank_protein_gi: 46361180 ) and PfFNR (genbank_protein_gi: 46361180 ) bind ( MI:0408 ) by comigration in sds page ( MI:0808 ) • MINT‐7043503 : PfFNR (genbank_protein_gi: 46361180 ) and PfFNR (genbank_protein_gi: 46361180 ) bind ( MI:0408 ) by molecular sieving ( MI:0071 ) • MINT‐7043886 , MINT‐7051941 : PfFd (uniprotkb: Q8IED5 ) and PfFNR (genbank_protein_gi: 46361180 ) enzymaticly react ( MI:0414 ) by enzymatic studies ( MI:0415 ) • MINT‐7051926 : PfFNR (genbank_protein_gi: 46361180 ) and PfFd (uniprotkb: Q8IED5 ) enzymaticly react ( MI:0414 ) by biophysical ( MI:0013 )