Structure and regulation of a Candida albicans alcohol dehydrogenase gene
A cDNA encoding Candida albicans alcohol dehydrogenase was isolated from a C. albicans expression library constructed from mRNA from C. albicans growing under conditions favouring the hyphal form. The library was screened for sequences that encoded immunogenic proteins using sera from patients with oral candidosis. The corresponding gene was isolated from a C. albicans genomic library by colony hybridisation using the cDNA as a probe. The 5'-promoter region was identified and the CADH1 gene and promoter were sequenced. The coding sequence is 1,050 bp long and the CADH1 gene has strong homology at the DNA level (75% to 56%) and high similarity (over 84%) at the amino acid level to the Adh proteins from Saccharomyces cerevisiae, Kluveromyces lactis and Schizosaccharomyces pombe. Analysis of the amino acid sequence showed that the deducted CAdhI protein contained highly conserved residues and a zinc-binding consensus associated with alcohol dehydrogenases. Southern blotting of C. albicans genomic DNA revealed a single band suggesting that a single alcohol dehydrogenase gene exists per haploid genome. The start site(s) for the CADH1 mRNA were determined and two major start sites and eight minor start were identified. Studies on the expression of the CADH1 gene showed that its mRNA was expressed at a high level on glucose-containing medium and that the CADH1 gene was regulated during batch growth on glucose and in response to carbon source. The CADH1 gene complemented a S. cerevisiae adh mutant and allowed transformants to grow on both glucose and ethanol-containing medium.