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

Radioiodination of rat-derived Pneumocystis carinii obtained from an in vitro culture demonstrated the presence of a major surface glycoprotein (gp120). 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 10(6). Surface 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.