Glycoproteins of Pneumocystis carinii: characterization by electrophoresis and microscopy

Glycoproteins are integral components of cell-surface structure and participate in adherence of pathogenic microbes to host cells. We have initiated studies of the glycoproteins of Pneumocystis carinii. Biotin-conjugated lectins, followed by reaction with avidin-peroxidase, were used to detect glycoproteins in electrophoretically separated proteins of P. carinii and on whole organisms when using light microscopy. Glycoproteins of P. carinii were clearly different from rat cell glycoproteins. Multiple glycoproteins were present in P. carinii and exhibited intense reactivity to both concanavalin A and wheat-germ agglutinin. Those lectins that reacted with the electrophoretically separated proteins also stained both alcohol-fixed P. carinii and the extracellular granular material present only in P. carinii preparations. In electron micrographs of P. carinii, which were stained with colloidal-gold-labeled concanavalin A, we found that the lectin bound to the outer surface of the organisms and to the tubular extensions emanating from the exterior surface.