title: Inverted topology of the Toxoplasma gondii ROP5 rhoptry protein provides new insights into the association of the ROP2 protein family with the parasitophorous vacuole membrane.
abstract: Toxoplasma gondii, as many intracellular parasites, is separated from the cytosol of its host cell by a parasitophorous vacuole membrane (PVM). This vacuole forms during host cell invasion and parasite apical organelles named rhoptries discharge proteins that associate with its membrane during this process. We report here the characterization of the rhoptry protein ROP5, which is a new member of the ROP2 family. Contrasting with what is known for other ROP2 family proteins, ROP5 is not processed during trafficking to rhoptries. We show here that ROP5 is secreted during invasion and associates with the PVM. Using differential permeabilization of infected cells, we have shown that ROP5 exposes its C-terminus towards the host cell cytoplasm, which corresponds to a reverse topology compared with ROP2 and ROP4. Taken together with recent modelling data suggesting that the C-terminal hydrophobic domain hitherto described as transmembrane may correspond to a hydrophobic helix buried in the catalytic domain of kinase-related proteins, these findings call for a reappraisal of the current view of ROP2 family proteins association with the PVM.
authors.affiliation: UMR5539 CNRS, Université de Montpellier 2, Place E Bataillon, 34095 Montpellier, France.
authors.forename: Hiba
authors.initials: H
authors.lastname: El Hajj
authors.forename: Maryse
authors.initials: M
authors.lastname: Lebrun
authors.forename: Marie Noëlle
authors.initials: MN
authors.lastname: Fourmaux
authors.forename: Henri
authors.initials: H
authors.lastname: Vial
authors.forename: Jean François
authors.initials: JF
authors.lastname: Dubremetz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism / Q000469:parasitology; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D014122:Toxoplasma / Q000737:chemistry* / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism* / Q000469:parasitology
chemical_list: D008565:Membrane Proteins; D015800:Protozoan Proteins; C090555:ROP 2 protein, Toxoplasma gondii; C516362:ROP4 protein, Toxoplasma gondii; D011994:Recombinant Proteins