Apicomplexa are protozoan parasites responsible for infective diseases of major worldwide impact, like malaria or toxoplasmosis. We have identified and characterized a redox system of Toxoplasma gondii (1), comprising ferredoxin-NADP+ reductase and ferredoxin, which is of vegetal origin and has not a homolog in the human host, thus being possibly a novel drug target (2). This system is localized in the apicoplast, an organelle shown to be essential for parasite survival both in P. falciparum and T. gondii. Recently, we have demonstrated the ability of the redox system FNR/Fd of P. falciparum to reconstitute in vitro the electron transfer pathway to the enzyme LytB which catalyzes the last step of the mevalonate-independent isoprenoid biosynthesis in the apicoplast (3). Here, we report a thorough characterization of the ferredoxin-NADP+ reductase of P. falciparum (PfFNR). We have cloned and overproduced in Escherichia coli the PfFNR in soluble and active form. The recombinant PfFNR, purified to homogeneity, has been studied with respect to the spectral properties and the interaction with its protein partner P. falciparum ferredoxin. Steady-state and rapid kinetics studies show several differences between the P. falciparum redox system and those of both plants and T.gondii. Redox titration experiments indicate that redox potential of the FAD prosthetic group of PfFNR is by far more positive than that of photosynthetic FNRs. Inhibition studies with organic and transition metal salts are in progress as well as the screening of conditions to obtain crystals for X-ray structure analysis. 1 Pandini V., Caprini G., Thomsen N., Aliverti A., Seeber F., Zanetti G. (2002) J. Biol. Chem. 277, 48463-48471. 2 Seeber F., Aliverti A., Zanetti G. (2005) Curr. Pharm. Des. 11, 3159-3172. 3 Rohrich RC, Englert N, Troschke K, Reichenberg A, Hintz M, Seeber F, Balconi E, Aliverti A, Zanetti G, Kohler U, Pfeiffer M, Beck E, Jomaa H, Wiesner J. (2005) FEBS Lett. 579,6433-8.
Functional characterization of Plasmodium falciparum ferredoxin-NADP+ reductase / E. Balconi, A. Pennati, E. Grassi, V. Pandini, F. Seeber, A. Aliverti, G. Zanetti. ((Intervento presentato al 1. convegno Trends in Enzymology tenutosi a Como nel 2006.
Functional characterization of Plasmodium falciparum ferredoxin-NADP+ reductase
E. BalconiPrimo
;A. PennatiSecondo
;E. Grassi;V. Pandini;A. AlivertiPenultimo
;G. ZanettiUltimo
2006
Abstract
Apicomplexa are protozoan parasites responsible for infective diseases of major worldwide impact, like malaria or toxoplasmosis. We have identified and characterized a redox system of Toxoplasma gondii (1), comprising ferredoxin-NADP+ reductase and ferredoxin, which is of vegetal origin and has not a homolog in the human host, thus being possibly a novel drug target (2). This system is localized in the apicoplast, an organelle shown to be essential for parasite survival both in P. falciparum and T. gondii. Recently, we have demonstrated the ability of the redox system FNR/Fd of P. falciparum to reconstitute in vitro the electron transfer pathway to the enzyme LytB which catalyzes the last step of the mevalonate-independent isoprenoid biosynthesis in the apicoplast (3). Here, we report a thorough characterization of the ferredoxin-NADP+ reductase of P. falciparum (PfFNR). We have cloned and overproduced in Escherichia coli the PfFNR in soluble and active form. The recombinant PfFNR, purified to homogeneity, has been studied with respect to the spectral properties and the interaction with its protein partner P. falciparum ferredoxin. Steady-state and rapid kinetics studies show several differences between the P. falciparum redox system and those of both plants and T.gondii. Redox titration experiments indicate that redox potential of the FAD prosthetic group of PfFNR is by far more positive than that of photosynthetic FNRs. Inhibition studies with organic and transition metal salts are in progress as well as the screening of conditions to obtain crystals for X-ray structure analysis. 1 Pandini V., Caprini G., Thomsen N., Aliverti A., Seeber F., Zanetti G. (2002) J. Biol. Chem. 277, 48463-48471. 2 Seeber F., Aliverti A., Zanetti G. (2005) Curr. Pharm. Des. 11, 3159-3172. 3 Rohrich RC, Englert N, Troschke K, Reichenberg A, Hintz M, Seeber F, Balconi E, Aliverti A, Zanetti G, Kohler U, Pfeiffer M, Beck E, Jomaa H, Wiesner J. (2005) FEBS Lett. 579,6433-8.
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