Functional analysis of Toxoplasma gondii protease inhibitor 1.
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 protease. 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.
Morris
Meredith Teilhet
MT
The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA.
Coppin
Alexandra
A
Tomavo
Stanislas
S
Carruthers
Vern B
VB
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005089:Exocytosis / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000469:parasitology; D006801:Humans; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015842:Serine Proteinase Inhibitors / Q000235:genetics / Q000378:metabolism*; D014122:Toxoplasma / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D014357:Trypsin / Q000378:metabolism
D015800:Protozoan Proteins; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; C412510:TgPI protein, Toxoplasma gondii; D014357:Trypsin; D002118:Calcium