Dual targeting of antioxidant and metabolic enzymes to the mitochondrion and the apicoplast of Toxoplasma gondii.
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.
Pino
Paco
P
Department of Microbiology and Molecular Medicine, Centre Medical Universitaire, University of Geneva, Geneva, Switzerland.
Foth
Bernardo Javier
BJ
Kwok
Lai-Yu
LY
Sheiner
Lilach
L
Schepers
Rebecca
R
Soldati
Thierry
T
Soldati-Favre
Dominique
D
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