ApiLoc - A database of published protein sub-cellular localisation in Apicomplexa

version 3 (curated until May 28, 2011)

Differential membrane targeting of the secretory proteins GRA4 and GRA6 within the parasitophorous vacuole formed by Toxoplasma gondii.

Labruyere, E., Lingnau, M., Mercier, C., Sibley, L. D. (1999 Aug 20, Mol Biochem Parasitol)

Following secretion into the parasitophorous vacuole, dense granule proteins, referred to as GRA proteins, are targeted to different locations including a complex of tubular membranes that are connected with the vacuolar membrane. To further define the formation of this intravacuolar network, we have investigated the secretion, trafficking and membrane association of GRA4 and GRA6 within the parasitophorous vacuole. In extracellular parasites, GRA4 and GRA6 were found exclusively in dense secretory granules where they were packaged primarily as soluble proteins. Following release into the vacuole, GRA6 was rapidly translocated to the posterior end of the parasite where, like previously reported for GRA2, it bound to a cluster of multi-lamellar vesicles that give rise to the network. In contrast, GRA4 was distributed throughout the lumen of the vacuole and only later became associated with the mature network that is found dispersed throughout the vacuole. Cell fractionation and treatment with denaturing agents established that the association of GRA4 with the network membranes was mediated by strong protein-protein interactions. In contrast, GRA6 was predominantly influenced by hydrophobic interactions, and a phosphorylated form of this protein present within the vacuole showed increased association with the network membranes. Cross-linking studies established that GRA4 and GRA6 specifically interact with GRA2 to form a multimeric complex that is stably associated with the intravacuolar network. Formation of this protein complex, which is based on both protein-protein and hydrophobic interactions, may participate in nutrient or protein transport within the vacuole.

PubMed: 10498186, full text

Localisation information

TGME49_027620 (GRA2) 28 kDa antigen

Experimental localisation: dense granule during extracellular tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "GRA2, GRA4 and GRA6 are colocalized in dense granules"
  • Microscopy type: EM
  • Microscopy method: Monoclonal antibody directly to protein
  • Strain: RH
  • Gene model mapping comments: inferred from another publication
  • Localisation record: dense granule during extracellular tachyzoite

TGME49_110780 (GRA4) hypothetical protein

Experimental localisation: dense granule during extracellular tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "GRA2, GRA4 and GRA6 are colocalized in dense granules"
  • Microscopy type: EM
  • Microscopy method: antibody directly to protein
  • Strain: RH
  • Gene model mapping comments: inferred from another publication
  • Localisation record: dense granule during extracellular tachyzoite

TGME49_075440 (GRA6) granule antigen protein GRA6

Experimental localisation: dense granule during extracellular tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "GRA2, GRA4 and GRA6 are colocalized in dense granules"
  • Microscopy type: EM
  • Microscopy method: antibody directly to protein
  • Strain: RH
  • Gene model mapping comments: inferred from another publication
  • Localisation record: dense granule during extracellular tachyzoite