White T C, Miyasaki S H, Agabian N
Intercampus Program in Molecular Parasitology, University of California-San Francisco 94143-1204.
J Bacteriol. 1993 Oct;175(19):6126-33. doi: 10.1128/jb.175.19.6126-6133.1993.
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 SAP1 and SAP2 genes (previously referred to as CAP, PEP, or PRA). A genomic library was screened under low-stringency hybridization conditions with a polymerase chain reaction fragment from SAP1. In addition to clones of SAP1 and SAP2, a clone containing SAP3, 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 virulence and pathogenesis. All 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 Sap1 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.
白色念珠菌分泌的天冬氨酸蛋白酶（SAP基因的产物）被认为通过其对念珠菌黏附、侵袭及致病性的影响而在致病过程中发挥作用。从一株表达表型转换系统的白色念珠菌（WO-1）中，根据分子量和N端序列已鉴定出三种分泌型天冬氨酸蛋白酶。鉴定出的这三种蛋白质均代表三种不同蛋白酶同工酶之一的成熟形式，其中两种分别对应于最近克隆的SAP1和SAP2基因（以前称为CAP、PEP或PRA）。用来自SAP1的聚合酶链反应片段在低严谨度杂交条件下筛选基因组文库。除了SAP1和SAP2的克隆外，还鉴定并测序了一个含有新型第三个分泌蛋白酶基因SAP3的克隆。这三种天冬氨酸蛋白酶同工酶在一级序列和pI上存在差异，表明它们可能在致病性和发病机制中发挥不同作用。这三种蛋白酶均在同一菌株中表达。然而，蛋白酶的表达模式与细胞的转换表型相关。WO-1菌株的不透明细胞表达Sap1和Sap3，而同一菌株的白色细胞表达Sap2。三种Sap蛋白酶的差异表达可能在白色念珠菌的致病过程中起作用。
