title: The malaria parasite Plasmodium falciparum has only one pyruvate dehydrogenase complex, which is located in the apicoplast.
abstract: The relict plastid (apicoplast) of apicomplexan parasites synthesizes fatty acids and is a promising drug target. In plant plastids, a pyruvate dehydrogenase complex (PDH) converts pyruvate into acetyl-CoA, the major fatty acid precursor, whereas a second, distinct PDH fuels the tricarboxylic acid cycle in the mitochondria. In contrast, the presence of genes encoding PDH and related enzyme complexes in the genomes of five Plasmodium species and of Toxoplasma gondii indicate that these parasites contain only one single PDH. PDH complexes are comprised of four subunits (E1alpha, E1beta, E2, E3), and we confirmed four genes encoding a complete PDH in Plasmodium falciparum through sequencing of cDNA clones. In apicomplexan parasites, many nuclear-encoded proteins are targeted to the apicoplast courtesy of two-part N-terminal leader sequences, and the presence of such N-terminal sequences on all four PDH subunits as well as phylogenetic analyses strongly suggest that the P. falciparum PDH is located in the apicoplast. Fusion of the two-part leader sequences from the E1alpha and E2 genes to green fluorescent protein experimentally confirmed apicoplast targeting. Western blot analysis provided evidence for the expression of the E1alpha and E1beta PDH subunits in blood-stage malaria parasites. The recombinantly expressed catalytic domain of the PDH subunit E2 showed high enzymatic activity in vitro indicating that pyruvate is converted to acetyl-CoA in the apicoplast, possibly for use in fatty acid biosynthesis.
authors.affiliation: Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Parkville, VIC 3010, Australia.
authors.forename: Bernardo J
authors.initials: BJ
authors.lastname: Foth
authors.forename: Luciana M
authors.initials: LM
authors.lastname: Stimmler
authors.forename: Emanuela
authors.initials: E
authors.lastname: Handman
authors.forename: Brendan S
authors.initials: BS
authors.lastname: Crabb
authors.forename: Anthony N
authors.initials: AN
authors.lastname: Hodder
authors.forename: Geoffrey I
authors.initials: GI
authors.lastname: McFadden
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D018076:DNA, Complementary / Q000737:chemistry; D016054:DNA, Protozoan / Q000737:chemistry; D004912:Erythrocytes / Q000469:parasitology; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics; D007438:Introns; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics; D018087:Plastids / Q000201:enzymology*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011768:Pyruvate Dehydrogenase Complex / Q000235:genetics / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D014122:Toxoplasma / Q000201:enzymology / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D016054:DNA, Protozoan; D021122:Protein Subunits; D011768:Pyruvate Dehydrogenase Complex; D049452:Green Fluorescent Proteins; D000105:Acetyl Coenzyme A; D019289:Pyruvic Acid