title: Characterization of a protein from Trypanosoma cruzi trypomastigotes that cleaves non-immune IgG bound through its Fab fragment.
abstract: A protein from Trypanosoma cruzi bloodstream trypomastigotes that binds IgG from man and several other animal species was isolated and characterized. The 52-kDa protein obtained from different T. cruzi cell extracts showed saturable binding with a K of 3.72 nM. Immunoblot analysis revealed that Fab, but not Fc, fragments of the Ig were recognized. When the protein was added to an unrelated C-fixation reaction, lysis was abolished in a dose-dependent fashion. When freshly prepared T. cruzi extracts were run in a 10% acrylamide SDS gel into which normal rabbit IgG was incorporated before polymerization, proteolytic activity, as seen by a transparent band after Coomassie blue staining, migrated in the same m.w. range of the 52-kDa protein. These data provide further clues to the mechanisms through which this pathogen escapes the host's immune response, thus maintaining a long-standing infection.
authors.affiliation: Ludwig Institute for Cancer Research, São Paulo, Brazil.
authors.forename: R M
authors.initials: RM
authors.lastname: Cicarelli
authors.forename: J D
authors.initials: JD
authors.lastname: Lopes
mesh_terms: D000818:Animals; D000915:Antibody Affinity; D001666:Binding Sites, Antibody; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000302:isolation & purification / Q000502:physiology; D002846:Chromatography, Affinity; D005260:Female; D006801:Humans; D006868:Hydrolysis; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism*; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008970:Molecular Weight; D011817:Rabbits; D014349:Trypanosoma cruzi / Q000032:analysis* / Q000502:physiology; D014357:Trypsin; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D014643:Variant Surface Glycoproteins, Trypanosoma; D014357:Trypsin