Monod M, Togni G, Hube B, Sanglard D
Laboratoire de Mycologie, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
Mol Microbiol. 1994 Jul;13(2):357-68. doi: 10.1111/j.1365-2958.1994.tb00429.x.
The secreted aspartic proteinases (SAP) of Candida sp. are presumed to be potential virulence factors. In the opportunistic pathogen Candida albicans the proteinase genes identified to date, SAP1, SAP2, SAP3 and SAP4, constitute a multigene family. Before addressing the possible role of each proteinase in virulence, we sought to isolate all the members of this multigene family by screening a genomic library with a SAP1 probe for additional C. albicans SAP genes using low-stringency hybridization conditions. Three putative new members, SAP5, SAP6 and SAP7 were isolated and sequenced. The N-terminal segments of the deduced amino acid sequences of SAP5 and SAP6 contained secretion signal sequences similar to those of other Candida SAPs. Upon comparison and alignment with the other reported SAP amino acid sequences, SAP7 is not only the most divergent protein but also exhibits a much longer putative pro-sequence with a single Lys-Lys putative processing site. Using SAP1 to SAP7 as probes, the overall number of SAP genes in C. albicans was tentatively estimated by low-stringency hybridization to EcoRI-digested genomic DNA. While each isolated SAP gene could be assigned to distinct EcoRI bands, the existence of two additional genes not isolated after screening of the C. albicans gene library was inferred. Furthermore, evidence was obtained for the existence of SAP multigene families in other Candida species such as C. tropicalis, C. parapsilosis and C. guillermondii.
念珠菌属的分泌型天冬氨酸蛋白酶（SAP）被认为是潜在的致病因子。在机会致病菌白色念珠菌中，迄今已鉴定出的蛋白酶基因SAP1、SAP2、SAP3和SAP4构成了一个多基因家族。在探讨每种蛋白酶在致病过程中可能发挥的作用之前，我们试图通过使用低严格度杂交条件，用SAP1探针筛选基因组文库以寻找白色念珠菌其他的SAP基因，从而分离出这个多基因家族的所有成员。分离并测序得到了三个假定的新成员SAP5、SAP6和SAP7。SAP5和SAP6推导氨基酸序列的N端片段含有与其他念珠菌属SAP相似的分泌信号序列。与其他已报道的SAP氨基酸序列进行比较和比对后发现，SAP7不仅是差异最大的蛋白，而且其假定的前体序列长得多，带有一个单一的Lys-Lys假定加工位点。以SAP1至SAP7为探针，通过对用EcoRI消化的基因组DNA进行低严格度杂交，初步估算了白色念珠菌中SAP基因的总数。虽然每个分离出的SAP基因可对应到不同的EcoRI条带，但推断在筛选白色念珠菌基因文库后还有另外两个未分离的基因存在。此外，还获得了证据，表明在其他念珠菌物种如热带念珠菌、近平滑念珠菌和季也蒙念珠菌中也存在SAP多基因家族。
