ROP2 from Toxoplasma gondii: a virulence factor with a protein-kinase fold and no enzymatic activity

Area of Science:

• Structural biology
• Parasitology
• Molecular biology

Background:

• The ROP2 protein and its paralogs are key virulence factors secreted by the parasite Toxoplasma gondii into host cells.
• Understanding the structure and function of these proteins is crucial for developing strategies against toxoplasmosis.

Purpose of the Study:

• To determine the crystal structure of a large, soluble domain of mature ROP2, representative of the ROP2-like protein family.
• To elucidate the structural basis for ROP2 function and membrane association.

Main Methods:

• X-ray crystallography was used to determine the three-dimensional structure of the ROP2 domain.
• Bioinformatic analysis and structural comparisons were performed.

Main Results:

• The structure reveals a protein-kinase fold that lacks essential catalytic residues and does not bind ATP.
• Unique structural extensions maintain the protein in an open conformation.
• The structure refutes a prior model of ROP2-like protein attachment to the parasitophorous vacuole membrane.

Conclusions:

• The ROP2 structure suggests it functions independently of kinase activity.
• A novel model for membrane attachment is proposed, involving basic and amphipathic helices in the N-terminus.
• This work provides new insights into the mechanism of virulence for Toxoplasma gondii.