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Open Access Publications from the University of California

Toxoplasma gondii: parasite glycosylation and an unusual cytochrome P450 enzyme of tissue cyst-forming coccidians

  • Author(s): Ochoa, Roxanna Jaimes
  • Advisor(s): Morrissette, Naomi
  • et al.

Toxoplasma gondii is an apicomplexan parasite that infects approximately thirty percent of the human population. As there is a need for new therapies, it is important to investigate Toxoplasma metabolic pathways to determine their role in parasite survival. In my first project, I used metabolic oligosaccharide engineering to profile glycosylated proteins in Toxoplasma tachyzoites. This approach uses metabolic incorporation of unnatural sugars into Toxoplasma proteins. My studies identified a variety of parasite proteins that are modified by glycans and validated modification of SAG1, a surface antigen in tachyzoite stage parasites. As β-elimination reduced the modified sugar signal, Ac4GlcNAz likely targets O-linked glycans in Toxoplasma. In a second study, I characterized a novel cytochrome P450 enzyme (CYP) in Toxoplasma. TgCYP localizes to the tachyzoite mitochondrion and has an unexpectedly restricted substrate: to date, it has only been shown to act on acetone. Although tgcyp null parasites have a modest growth defect when grown in competition with wild-type parasites, the null parasites have a robust growth advantage when 2% acetone is added to the culture conditions, suggesting that expressing TgCYP is deleterious under certain conditions.

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