Identification and isolation of a major cell surface glycoprotein of Pneumocystis carinii

Abstract

Radioiodination of rat-derived Pneumocystis carinii obtained from an in vitro culture demonstrated the presence of a major surface glycoprotein (gpl20). The glycoprotein was of the high-mannose type. It exhibited adherence properties similar to those observed in the intact organism. Under nonreducing conditions, it existed as an aggregate with a molecular weight in excess of 2 x 106. Since its aggregating behavior and adherent quality prevented isolation of the glycoprotein by conventional methods, the glycoprotein was purified by chromatography on hydroxyapatite in the presence of sodium dodecyl sulfate under reducing conditions.

Residence at the expression site is necessary and sufficient for the transcription of surface antigen genes of Pneumocystis carinii

“…All studied special forms of P. carinii are coated with a major surface glycoprotein (MSG) (Walzer and Linke, 1987;Kovacs et al, 1988;Pesanti and Shanley, 1988;Linke and Walzer, 1989;Radding et al, 1989;Tanabe et al, 1989;Lundgren et al, 1991), also known as gpA (Gigliotti et al, 1988;Gigliotti, 1992). In P. carinii special forms recovered from rats, ferrets, mice and humans, it has been shown that MSG is actually a family of proteins encoded by a family of heterogeneous genes (S.L.…”

Expression of variants of the major surface glycoprotein of Pneumocystis carinii.

“…While important differences exist in P. carinii organisms isolated from different hosts, all possess an abundant, highly immunogenic, major surface glycoprotein (MSG), also called gpA (4)(5)(6). MSG shows a size on reducing SDS-PAGE of between 95 and 120 kD (7).…”

VII. The major surface antigen of Pneumocystis carinii

“…Immunohistochemical analysis using anti-MSG monoclonal antibodies demonstrated that ferritin granules conjugated with these antibodies bound to the surface of the cyst as well as of the trophozoite of P. carinii [9]. Immunoblotting analysis of P. carinii proteins separated by SDS-polyacrylamide gel electrophoresis clearly showed that a major part of the total protein is seen in both cysts and trophozoites at 1051 20 kDa and that this major broad band is a common epitope to the anti-MSG monoclonal antibody [9,11].…”

“…Pneumocystis carinii are coated by abundant surface proteins of great interest to investigators [1^24]. The major protein components of both cysts and trophozoites are proteins called MSG (major surface glycoprotein; see [23^25]), P115 [9], gp120 [11] or gpA [19,20], with an apparent molecular mass ranging from 95 to 140 kDa, depending on host species, degree of glycosylation, and isolation procedures. The nomenclature for this antigen complex is somewhat confusing, and we refer to it here as MSG as it represents closely the nature of this antigen.…”