ROP18 is a rhoptry kinase controlling the intracellular proliferation of Toxoplasma gondii

PLoS Pathog. 2007 Feb;3(2):e14. doi: 10.1371/journal.ppat.0030014.


Toxoplasma gondii is an obligate intracellular parasite for which the discharge of apical organelles named rhoptries is a key event in host cell invasion. Among rhoptry proteins, ROP2, which is the prototype of a large protein family, is translocated in the parasitophorous vacuole membrane during invasion. The ROP2 family members are related to protein-kinases, but only some of them are predicted to be catalytically active, and none of the latter has been characterized so far. We show here that ROP18, a member of the ROP2 family, is located in the rhoptries and re-localises at the parasitophorous vacuole membrane during invasion. We demonstrate that a recombinant ROP18 catalytic domain (amino acids 243-539) possesses a protein-kinase activity and phosphorylate parasitic substrates, especially a 70-kDa protein of tachyzoites. Furthermore, we show that overexpression of ROP18 in transgenic parasites causes a dramatic increase in intra-vacuolar parasite multiplication rate, which is correlated with kinase activity. Therefore, we demonstrate, to our knowledge for the first time, that rhoptries can discharge active protein-kinases upon host cell invasion, which can exert a long-lasting effect on intracellular parasite development and virulence.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Catalytic Domain
  • Humans
  • Membrane Proteins / analysis
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / physiology*
  • Molecular Sequence Data
  • Protein Kinases / physiology*
  • Protozoan Proteins / analysis
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / genetics
  • Protozoan Proteins / physiology*
  • Scattering, Radiation
  • Toxoplasma / growth & development*
  • Toxoplasma / pathogenicity
  • Vacuoles / parasitology
  • Virulence
  • X-Rays


  • Membrane Proteins
  • Protozoan Proteins
  • ROP 2 protein, Toxoplasma gondii
  • Protein Kinases

Associated data

  • GENBANK/AF420596
  • GENBANK/AM056071
  • GENBANK/AM075204
  • GENBANK/CAA85377
  • GENBANK/CAA96467
  • GENBANK/DQ116423