title: GRA9, a new Toxoplasma gondii dense granule protein associated with the intravacuolar network of tubular membranes.
abstract: Important components of the parasitophorous vacuole in which the intracellular protozoan parasite Toxoplasma gondii develops, comprise proteins secreted from apicomplexan specific secretory organelles named the dense granules. Here, we confirm by immunofluorescence and by cryo-electron microscopy that the recently isolated B10 protein (318 amino acids, 41kDa) is a new dense granule protein that should now be referred to as GRA9. Within the vacuolar compartment, GRA9, like GRA2, GRA4 and GRA6, associates with the network of tubular membranes connected to the parasitophorous vacuole delimiting membrane. Like the other GRA proteins, GRA9 is secreted into the vacuole from the anterior end of the parasite. However, unlike GRA2 or GRA6, GRA9 does not transit by the posterior invaginated pocket of the parasite where the network first assembles. Within the dense granules, GRA9 exists in both a soluble and an insoluble state. Like the other GRA proteins, GRA9 is secreted as a soluble form only and like most of the GRA proteins, two forms of GRA9 of the similar molecular weight are detected within the vacuolar space: a soluble form and a membrane associated form. The dual properties of GRA9 are not only ascribed by the presence of amphipathic and hydrophobic alpha-helices but also by the fact that the protein is mainly hydrophilic.
authors.affiliation: Institute for Medical Microbiology and Virology, Universitätstr. 1, D-40225 Düsseldorf, Germany.
authors.forename: Koku D Z
authors.initials: KD
authors.lastname: Adjogble
authors.forename: Corinne
authors.initials: C
authors.lastname: Mercier
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Dubremetz
authors.forename: Christian
authors.initials: C
authors.lastname: Hucke
authors.forename: Colin R
authors.initials: CR
authors.lastname: Mackenzie
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Cesbron-Delauw
authors.forename: Walter
authors.initials: W
authors.lastname: Däubener
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000032:analysis*; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique / Q000379:methods; D057927:Hydrophobic and Hydrophilic Interactions; D007425:Intracellular Membranes / Q000469:parasitology; D016253:Microscopy, Immunoelectron / Q000379:methods; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000032:analysis*; D012995:Solubility; D014122:Toxoplasma / Q000737:chemistry*; D014617:Vacuoles / Q000469:parasitology
chemical_list: D000953:Antigens, Protozoan; C117859:B10 antigen, Toxoplasma gondii; D015800:Protozoan Proteins