The 43-kDa glycoprotein from the human pathogen Paracoccidioides brasiliensis and its deglycosylated form: excretion and susceptibility to proteolysis.
Biochemical properties of the concanavalin A-binding 43-kDa glycoprotein (gp43) of Paracoccidioides brasiliensis and its deglycosylated form were compared. Deglycosylation was achieved by treatment with trifluoromethanesulfonic acid, endoglycosidase H, N-glycanase, or metabolically, by growing cells with tunicamycin. The resulting antigen in all cases had Mr 38,000, and probably derived from the gp43 by loss of N-linked high-mannose oligosaccharide chains. The presence of galactopyranose units in the carbohydrate chains was suggested by antigen binding to peanut lectin. Pulse and chase experiments using [35S]methionine metabolic labeling of P. brasiliensis growing in the presence of tunicamycin showed that the N-linked chains of gp43 are not required for antigen secretion. The 38-kDa antigen was more susceptible than the native antigen to the action of papain and pronase, thus indicating a protective role of the carbohydrate moiety against proteolysis. Both forms are equally resistant to endogenous proteases at neutral pH. The gp43, itself, has a proteolytic activity at pH 5-6, but not at neutral pH. Deglycosylation with endoglycosidase H or tunicamycin preserved epitopes in the 38-kDa molecule reactive with (a) antibodies from patients with paracoccidioidomycosis, or rabbit immunized with the gp43 and (b) mouse monoclonal antibodies against the gp43 antigen. The present results provide a basis for the understanding of diagnostic reactions and fungal virulence involving the gp43 exocellular antigen of P. brasiliensis.
Puccia
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Disciplina de Biologia Celular, Escola Paulista de Medicina, São Paulo, Brazil.
Travassos
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LR
D000946:Antigens, Fungal; D005656:Fungal Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D006031:Glycosylation; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D010228:Paracoccidioides / Q000276:immunology / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000494:pharmacology; D011952:Receptors, Concanavalin A / Q000737:chemistry / Q000276:immunology / Q000378:metabolism
D000946:Antigens, Fungal; D005656:Fungal Proteins; D011952:Receptors, Concanavalin A; C027774:concanavalin A-binding glycoproteins; D010447:Peptide Hydrolases