Geber A, Williamson P R, Rex J H, Sweeney E C, Bennett J E
Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892.
J Bacteriol. 1992 Nov;174(21):6992-6. doi: 10.1128/jb.174.21.6992-6996.1992.
In order to isolate the structural gene involved in sucrose utilization, we screened a sucrose-induced Candida albicans cDNA library for clones expressing alpha-glucosidase activity. The C. albicans maltase structural gene (CAMAL2) was isolated. No other clones expressing alpha-glucosidase activity. were detected. A genomic CAMAL2 clone was obtained by screening a size-selected genomic library with the cDNA clone. DNA sequence analysis reveals that CAMAL2 encodes a 570-amino-acid protein which shares 50% identity with the maltase structural gene (MAL62) of Saccharomyces carlsbergensis. The substrate specificity of the recombinant protein purified from Escherichia coli identifies the enzyme as a maltase. Northern (RNA) analysis reveals that transcription of CAMAL2 is induced by maltose and sucrose and repressed by glucose. These results suggest that assimilation of sucrose in C. albicans relies on an inducible maltase enzyme. The family of genes controlling sucrose utilization in C. albicans shares similarities with the MAL gene family of Saccharomyces cerevisiae and provides a model system for studying gene regulation in this pathogenic yeast.
为了分离参与蔗糖利用的结构基因，我们筛选了一个由蔗糖诱导的白色念珠菌cDNA文库，以寻找表达α-葡萄糖苷酶活性的克隆。分离出了白色念珠菌麦芽糖酶结构基因（CAMAL2）。未检测到其他表达α-葡萄糖苷酶活性的克隆。通过用该cDNA克隆筛选一个大小选择的基因组文库，获得了一个基因组CAMAL2克隆。DNA序列分析表明，CAMAL2编码一个570个氨基酸的蛋白质，该蛋白质与卡尔斯伯酵母的麦芽糖酶结构基因（MAL62）有50%的同源性。从大肠杆菌中纯化的重组蛋白的底物特异性表明该酶是一种麦芽糖酶。Northern（RNA）分析表明，CAMAL2的转录受麦芽糖和蔗糖诱导，并受葡萄糖抑制。这些结果表明，白色念珠菌中蔗糖的同化依赖于一种可诱导的麦芽糖酶。控制白色念珠菌蔗糖利用的基因家族与酿酒酵母的MAL基因家族有相似之处，并为研究这种致病酵母中的基因调控提供了一个模型系统。
