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Title: Toxoplasma gondii: Biochemical and biophysical characterization of recombinant soluble dense granule proteins GRA2 and GRA6

The most prominent structural feature of the parasitophorous vacuole (PV) in which the intracellular parasite Toxoplasma gondii proliferates is a membranous nanotubular network (MNN), which interconnects the parasites and the PV membrane. The MNN function remains unclear. The GRA2 and GRA6 proteins secreted from the parasite dense granules into the PV have been implicated in the MNN biogenesis. Amphipathic alpha-helices (AAHs) predicted in GRA2 and an alpha-helical hydrophobic domain predicted in GRA6 have been proposed to be responsible for their membrane association, thereby potentially molding the MMN in its structure. Here we report an analysis of the recombinant proteins (expressed in detergent-free conditions) by circular dichroism, which showed that full length GRA2 displays an alpha-helical secondary structure while recombinant GRA6 and GRA2 truncated of its AAHs are mainly random coiled. Dynamic light scattering and transmission electron microscopy showed that recombinant GRA6 and truncated GRA2 constitute a homogenous population of small particles (6–8 nm in diameter) while recombinant GRA2 corresponds to 2 populations of particles (∼8–15 nm and up to 40 nm in diameter, respectively). The unusual properties of GRA2 due to its AAHs are discussed. - Highlights: • Toxoplasma gondii: soluble GRA2 forms 2 populations of particles. • T. gondii: the dense granulemore » protein GRA2 folds intrinsically as an alpha-helix. • T. gondii: monomeric soluble GRA6 forms particles of 6–8 nm in diameter. • T. gondii: monomeric soluble GRA6 is random coiled. • Unusual biophysical properties of the dense granule protein GRA2 from T. gondii.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [4] ; ; ;  [1] ;  [2] ; ;  [3] ;  [2] ;  [2] ;  [4] ; ;  [1] ;  [2] ;  [1] ;  [2]
  1. CNRS, UMR 5163, 38042 Grenoble (France)
  2. (France)
  3. Université Grenoble Alpes, Institut de Biologie Structurale (IBS), 38044 Grenoble (France)
  4. (UVHCI), UMI 3265 (UJF-EMBL-CNRS), 38027 Grenoble (France)
Publication Date:
OSTI Identifier:
22461979
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemical and Biophysical Research Communications; Journal Volume: 459; Journal Issue: 1; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; AMINO ACIDS; DETERGENTS; DICHROISM; LIGHT SCATTERING; MANGANESE NITRIDES; MEMBRANES; MONOCLONAL ANTIBODIES; PARASITES; PARTICLES; PROTEINS; RANDOMNESS; TRANSMISSION ELECTRON MICROSCOPY