Our primary interest is the study of biochemical mechanisms of the obligate intracellular parasite, Toxoplasma gondii. This protozoan parasite infects an estimated one-third of North-Americans and is probably one of the most wide-spread parasite on earth. In general, the infections in healthy adults are usually asymptomatic. However, the infections in neonates and immuno-compromised individuals can be devastating. T.gondii is indeed the causative agent of congenital toxoplasmosis, the leading cause of neurological birth defects, and toxoplasmic encephalitis the most common cause of focal brain lesions in AIDS patients.