Wall formation by Candida albicans yeast cells: synthesis, secretion and incorporation of two types of mannoproteins.

The mannoprotein components solubilized from the walls of Candida albicans blastoconidia following degradation of the glucan network with beta-glucanase (Zymolyase) have higher molecular masses than their probable precursors present in the supernatant of regenerating protoplasts. It therefore appears that the mannoproteins are released from the walls as part of supramolecular complexes. Immunological analysis using both polyclonal and monoclonal antibodies has demonstrated the probable relationship between molecules found in a mixed membrane preparation, those secreted by regenerating protoplasts, and those present in yeast cell walls. Some mannoproteins secreted by protoplasts incubated in the presence of tunicamycin had significantly increased mobility on SDS-PAGE, whereas others were not affected by the treatment. It is therefore possible that two types of mannoproteins are secreted by protoplasts: one carrying N-glycosylated chains (mannan) and one lacking them. All the proteins secreted in the presence of tunicamycin stained with Concanavalin A-peroxidase, demonstrating that they all, including the N-glycosylated ones, carried O-glycosylated sugar residues. Both classes of mannoproteins, secreted independently of each other, were found in the molecular complexes rendered soluble from the wall by Zymolyase digestion. Data obtained with a monoclonal antibody demonstrated the presence of a repeated epitope within one wall protein(s) detectable in a mixed membrane preparation and in the wall complexes released by Zymolyase.