Effect of papulacandin B and calcofluor white on the incorporation of mannoproteins in the wall of Candida albicans blastospores.

Incorporation of mannoproteins into the walls of Candida albicans blastospores (yeast phase) was followed by continuous labelling and pulse-chase experiments. The effect in the process of compounds that interfere with synthesis (papulacandin B) or assembly (calcofluor white) of structural polymers was also assessed. Mannoproteins which are kept in place by non-covalent bonds (mainly hydrogen bonds) were incorporated rapidly after their release into the periplasmic space, this process being blocked by calcofluor white. The stain had no effect on the incorporation of covalently linked mannoproteins. Papulacandin B inhibited formation of beta-glucans and incorporation of covalently linked mannoprotein molecules, whereas incorporation of hydrogen-bonded species took place normally. The results suggest that the formation of the non-covalent bonds between the mannoproteins occurs once they are secreted into the periplasmic space, whereas the formation of covalent connections between mannoproteins and wall glucan takes place at the level of the plasma membrane.