Candida albicans

The secreted aspartyl proteinases of Candida albicans (products of the SAP genes) are thought to contribute to virulence through their effects on Candida adherence, invasion, and pathogenicity. From a single strain of C. albicans (WO-1) which expresses a phenotypic switching system, three secreted aspartyl proteinases have been identified as determined by molecular weight and N-terminal sequence. Each of the three identified proteins represents the mature form of one of three distinct proteinase isoenzymes, two of which correspond to the recently cloned SAP) and SAP2 genes (previously referred to as CAP, PEP, or PR4). A genomic library was screened under low-stringency hybridization conditions with a polymerase chain reaction f ent from SAP). In addition to clones ofSAP) and SAP2, a done containing S4P3, a novel third secreted proteinase gene, was identified and sequenced. The three aspartyl proteinase isoenzymes differ in primary sequence and pI, suggesting that they may play different roles in virlence and pathogenesis. AU three of these proteinases are expressed in the same strain. However, the pattern of proteinase expression is correlated with the switch phenotype of the cell. Opaque cells of strain WO-1 express Sapl and Sap3, while white cells of the same strain express Sap2. The differential expression of three Sap proteinases may contribute to virulence in C. albicans.