Identification of a mitochondrial superoxide dismutase with an unusual targeting sequence in Plasmodium falciparum |
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Authors: | Sienkiewicz Natasha Daher Wassim Dive Daniel Wrenger Carsten Viscogliosi Eric Wintjens René Jouin Helène Capron Monique Müller Sylke Khalife Jamal |
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Affiliation: | Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, WTB/MSI Complex, DD15EH, UK. |
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Abstract: | The intraerythrocytic stages of Plasmodium falciparum are exposed to oxidative stress and require functional anti-oxidant systems to survive. In addition to the parasite's known iron-dependent superoxide dismutase PfSOD1, a second SOD gene (PfSOD2) interrupted by 8 introns was identified on chromosome 6. Molecular modelling shows that the structure of PfSOD2 is similar to other iron-dependent SODs and phylogenetic analysis suggests PfSOD1 and PfSOD2 are the result of an ancestral gene duplication. The deduced amino acid sequence of PfSOD2 is similar to PfSOD1 but has a long N-terminal extension. Immunofluorescence studies show that PfSOD1 is cytosolic, whereas the N-terminal extension of PfSOD2 targets a green fluorescent protein fusion into the parasite's mitochondrion. Both SOD genes are transcribed during the erythrocytic cycle with PfSOD1 mRNA levels up to 35-fold higher than those of PfSOD2. Northern blots demonstrated that the mRNA levels of both SOD genes are up-regulated upon exposure to oxidative stress. |
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