Trypanosoma cruzi: identification of a membrane cysteine proteinase linked through a GPI anchor.
The biochemical and functional properties of T. cruzi GP50/55, a novel glycosylphosphatidylinositol (GPI)-anchored membrane antigen have been investigated. A 50-52-kDa thiol proteinase activity could be immunoprecipitated with monoclonal antibodies (mAb) directed against GP50/55 (mAb C10), different from the one reactive with mAbs against lysosomal cysteine proteinase GP57/51. Furthermore, the mAb C10-reactive proteinase corresponded to the GPI-anchored surface antigen since the proteolytic and antigenic activity partitioned to the aqueous phase after Triton X114 phase separation of phosphatidylinositol specific phospholipase C (PI-PLC)-treated parasites. Of several proteins immunoprecipitated by a polyclonal anti-lysosomal cysteine proteinase, an mAb to GP57/51 recognized a 60-kDa protein, whereas mAb C10 recognized antigens ranging between 52 and 50 kDa. The GP50/55 antigen detected by mAb C10 is expressed on the parasite surface whereas the GP57/51 antigen is mainly intracellular. The internal peptide sequence obtained from purified GP50/55 showed that it is more homologous to the prototype of the cysteine proteinases superfamily, papain, than to the two T. cruzi lysosomal cysteine proteinases so far described. Our data indicate that the T. cruzi GP50/55 is a novel GPI-anchored cysteine proteinase and may represent another isoform of this heterogeneous group of proteinases.
Fresno
M
M
Centro de Biología Molecular, Universidad Autónoma de Madrid, Spain.
Hernández-Munaín
C
C
de-Diego
J
J
Rivas
L
L
Scharfstein
J
J
Bonay
P
P
D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry* / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D005434:Flow Cytometry; D006023:Glycoproteins / Q000737:chemistry* / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000737:chemistry* / Q000378:metabolism; D011233:Precipitin Tests; D014349:Trypanosoma cruzi / Q000737:chemistry* / Q000378:metabolism
D000953:Antigens, Protozoan; D006023:Glycoproteins; D017261:Glycosylphosphatidylinositols; D003546:Cysteine Endopeptidases