Studies on palmitoylation in Toxoplasma gondii

DE NAPOLI MG, DE MIGUEL N, ANGEL SO AND CORVI MM

Cordoba

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

Palmitoylation is a post-translational modification which provides proteins with enough hydrophobicity to interact with membranes. In Toxoplasma gondii, little is known of this important modification. Metabolic labeling of T. gondii tachyzoites with [3H]-palmitic acid revealed several radioactive proteins that are modified with this fatty acid, indicating that protein palmitoylation occurs in this parasite. Furthermore, incubation of T. gondii tachyzoites with a palmitoylation inhibitor 2-Br-palmitate blocked the invasion process. In addition, we identified TgHSP20, a small heat shock protein, to be palmitoylated “in vivo” in T. gondii. TgHSP20 is a stripe-arranged chaperone localized to the inner membrane complex (IMC) of the parasite. TgHSP20 association to the IMC is quite striking since the protein does not contain any hydrophobic region or transmembrane domains. Compared alignment of HSP20 aminoacidic sequences from different apicomplexa parasites revealed a set of cisteines that are conserved among them. Interestingly, these conserved cisteine- residues are predicted to be palmitoylated by “in silico” analysis. Taken together, the data obtained shows that protein palmitoylation is an operating system in T. gondii that may be of importance in the parasite invasion process. Besides, we have started to identify proteins that are palmitoylated in this parasite.