The 43-kDa glycoprotein from the human pathogen Paracoccidioides brasiliensis and its deglycosylated form: excretion and susceptibility to proteolysis.

Abstract

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.

• Authors: R Puccia, L R Travassos
• Journal: Archives of biochemistry and biophysics (Arch Biochem Biophys) Vol. 289 Issue 2 Pg. 298-302 (Sep 1991) ISSN: 0003-9861 [Print] United States
• PMID: 1898073 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antigens, Fungal
• Fungal Proteins
• Receptors, Concanavalin A
• concanavalin A-binding glycoproteins
• Peptide Hydrolases

Topics

• Antigens, Fungal
• Fungal Proteins (chemistry, immunology, metabolism)
• Glycosylation
• Hydrogen-Ion Concentration
• Molecular Weight
• Paracoccidioides (immunology, metabolism)
• Peptide Hydrolases (pharmacology)
• Receptors, Concanavalin A (chemistry, immunology, metabolism)