title: Targeting of the ring exported protein 1 to the Maurer's clefts is mediated by a two-phase process.
abstract: Early development of Plasmodium falciparum within the erythrocyte is characterized by the large-scale export of proteins to the host cell. In many cases, export is mediated by a short sequence called the Plasmodium export element (PEXEL) or vacuolar transport signal; however, a number of previously characterized exported proteins do not contain such an element. In this study, we investigated the mechanisms of export of the PEXEL-negative ring exported protein 1 (REX1). This protein localizes to the Maurer's clefts, parasite-induced structures in the host-cell cytosol. Transgenic parasites expressing green fluorescent protein-REX1 chimeras revealed that the single hydrophobic stretch plus an additional 10 amino acids mediate the export of REX1. Biochemical characterization of these chimeras indicated that REX1 was exported as a soluble protein. Inclusion of a sequence containing a predicted coiled-coil motif led to the correct localization of REX1 at the Maurer's clefts, suggesting that association with the clefts occurs at the final stage of protein export only. These results indicate that PEXEL-negative exported proteins can be exported in a soluble state and that sequences without any apparent resemblance to a PEXEL motif can mediate export across the parasitophorous vacuole membrane.
authors.affiliation: Malaria Biology Laboratory, Queensland Institute of Medical Research, Herston, QLD, Australia.
authors.forename: Matthew W A
authors.initials: MW
authors.lastname: Dixon
authors.forename: Paula L
authors.initials: PL
authors.lastname: Hawthorne
authors.forename: Tobias
authors.initials: T
authors.lastname: Spielmann
authors.forename: Karen L
authors.initials: KL
authors.lastname: Anderson
authors.forename: Katharine R
authors.initials: KR
authors.lastname: Trenholme
authors.forename: Donald L
authors.initials: DL
authors.lastname: Gardiner
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D003600:Cytosol / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D004912:Erythrocytes / Q000469:parasitology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010963:Plasmodium falciparum / Q000378:metabolism* / Q000502:physiology*; D021381:Protein Transport; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism*; D014162:Transfection; D014617:Vacuoles / Q000378:metabolism
chemical_list: D017931:DNA Primers; D015800:Protozoan Proteins; D049452:Green Fluorescent Proteins