Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 277, Issue 47, Pages 45259-45266Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M205517200
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- NIAID NIH HHS [AI074417-06, R01 AI046675] Funding Source: Medline
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We have characterized a Kazal family serine protease inhibitor, Toxoplasma gondii protease inhibitor 1 (TgPI-1), in the obligate intracellular parasite Toxoplasma gondii. TgPI-1 contains four inhibitor domains predicted to inhibit trypsin, chymotrypsin, and elastase. Antibodies against recombinant TgPI-1 detect two polypeptides, of 43 and 41 kDa, designated TgPI-1(43) and TgPI-1(41), in tachyzoites, bradyzoites, and sporozoites. TgPI-1(43) and TgPI-1(41) are secreted constitutively from dense granules into the excreted/secreted antigen fraction as well as the parasitophorous vacuole that T. gondii occupies during intracellular replication. Recombinant TgPI-1 inhibits trypsin, chymotrypsin, pancreatic elastase, and neutrophil elastase. Immunoprecipitation studies with anti-rTgPI-1 antibodies reveal that recombinant TgPI-1 forms a complex with trypsin that is dependent on interactions with the active site of the pro- tease. TgPI-1 is the first anti-trypsin/chymotrypsin inhibitor to be identified in bradyzoites and sporozoites, stages of the parasite that would be exposed to proteolytic enzymes in the digestive tract of the host.
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