title: Dual targeting of antioxidant and metabolic enzymes to the mitochondrion and the apicoplast of Toxoplasma gondii.
abstract: Toxoplasma gondii is an aerobic protozoan parasite that possesses mitochondrial antioxidant enzymes to safely dispose of oxygen radicals generated by cellular respiration and metabolism. As with most Apicomplexans, it also harbors a chloroplast-like organelle, the apicoplast, which hosts various biosynthetic pathways and requires antioxidant protection. Most apicoplast-resident proteins are encoded in the nuclear genome and are targeted to the organelle via a bipartite N-terminal targeting sequence. We show here that two antioxidant enzymes-a superoxide dismutase (TgSOD2) and a thioredoxin-dependent peroxidase (TgTPX1/2)-and an aconitase are dually targeted to both the apicoplast and the mitochondrion of T. gondii. In the case of TgSOD2, our results indicate that a single gene product is bimodally targeted due to an inconspicuous variation within the putative signal peptide of the organellar protein, which significantly alters its subcellular localization. Dual organellar targeting of proteins might occur frequently in Apicomplexans to serve important biological functions such as antioxidant protection and carbon metabolism.
authors.affiliation: Department of Microbiology and Molecular Medicine, Centre Medical Universitaire, University of Geneva, Geneva, Switzerland.
authors.forename: Paco
authors.initials: P
authors.lastname: Pino
authors.forename: Bernardo Javier
authors.initials: BJ
authors.lastname: Foth
authors.forename: Lai-Yu
authors.initials: LY
authors.lastname: Kwok
authors.forename: Lilach
authors.initials: L
authors.lastname: Sheiner
authors.forename: Rebecca
authors.initials: R
authors.lastname: Schepers
authors.forename: Thierry
authors.initials: T
authors.lastname: Soldati
authors.forename: Dominique
authors.initials: D
authors.lastname: Soldati-Favre
mesh_terms: D000154:Aconitate Hydratase / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D017931:DNA Primers / Q000737:chemistry; D016054:DNA, Protozoan / Q000032:analysis; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D010544:Peroxidases / Q000378:metabolism*; D016415:Sequence Alignment; D013482:Superoxide Dismutase / Q000378:metabolism*; D014122:Toxoplasma / Q000166:cytology* / Q000201:enzymology* / Q000235:genetics