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

version 3 (curated until May 28, 2011)

Transmembrane domain modulates sorting of membrane proteins in Toxoplasma gondii.

Karsten, V., Hegde, R. S., Sinai, A. P., Yang, M., Joiner, K. A. (2004 Jun 18, J Biol Chem)

Overlapping mechanisms that function simultaneously in the intracellular sorting of mammalian membrane proteins often confound delineation of individual sorting pathways. By analyzing sorting in the evolutionarily simpler organism Toxoplasma gondii, we demonstrate a role for transmembrane domain (TMD) length in modulating the signal-dependent segregation of membrane proteins to distinct intracellular organelles. The dense granule localization of the single pass transmembrane protein GRA4 could be completely rerouted to the Golgi and cell surface simply by replacement of its TMD with that from either vesicular stomatitis virus G or the low density lipoprotein (LDL) receptor. Mutational and biochemical analyses suggested that this effect was not caused by any specific sequence motif or strength of membrane association of the GRA4 TMD. Instead, a property imparted by the vesicular stomatitis virus G or LDL receptor TMDs, both of which are longer than the GRA4 TMD, appeared to be a decisive factor. Indeed, shortening the LDL receptor TMD to a length similar to that of GRA4 resulted in dense granule localization, whereas lengthening the GRA4 TMD resulted in rerouting to the Golgi. From these data, we conclude that although the TMD may not necessarily be a sole determinant in membrane protein sorting, its properties can markedly modulate the utilization of more conventional signal-mediated sorting pathways.

PubMed: 15056659, full text

Localisation information

TGME49_110780 (GRA4) hypothetical protein

Experimental localisation: dense granule during tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "shortening the LDL receptor TMD to a length similar to that of GRA4 resulted in dense granule localization, whereas lengthening the GRA4 TMD resulted in rerouting to the Golgi."
  • Microscopy type: Light
  • Microscopy method: BAP tag
  • Strain: RH
  • Gene model mapping comments: inferred from another publication
  • Localisation record: dense granule during tachyzoite
  • Comment: BAP fused to the cytosolic tail of the protein, not the whole endogenous protein