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Intramembrane cleavage of microneme proteins at the surface of the apicomplexan parasite Toxoplasma gondii
Author(s) -
Opitz Corinna,
Cristina Manlio Di,
Reiss Matthias,
Ruppert Thomas,
Crisanti Andrea,
Soldati Dominique
Publication year - 2002
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/21.7.1577
Subject(s) - microneme , biology , toxoplasma gondii , parasite hosting , apicomplexa , protozoa , cleavage (geology) , dense granule , microbiology and biotechnology , genetics , protozoal disease , immunology , antibody , paleontology , fracture (geology) , malaria , world wide web , computer science
Apicomplexan parasites actively secrete proteins at their apical pole as part of the host cell invasion process. The adhesive micronemal proteins are involved in the recognition of host cell receptors. Redistribution of these receptor–ligand complexes toward the posterior pole of the parasites is powered by the actomyosin system of the parasite and is presumed to drive parasite gliding motility and host cell penetration. The microneme protein protease termed MPP1 is responsible for the removal of the C‐terminal domain of TgMIC2 and for shedding of the protein during invasion. In this study, we used site‐specific mutagenesis to determine the amino acids essential for this cleavage to occur. Mapping of the cleavage site on TgMIC6 established that this processing occurs within the membrane‐spanning domain, at a site that is conserved throughout all apicomplexan microneme proteins. The fusion of the surface antigen SAG1 with these transmembrane domains excluded any significant role for the ectodomain in the cleavage site recognition and provided evidence that MPP1 is constitutively active at the surface of the parasites, ready to sustain invasion at any time.