Candida albicans Estrogen-Binding Protein Gene Encodes an Oxidoreductase that is Inhibited by Estradiol

• Published in: Proceedings of the National Academy of Sciences - PNAS 1994-02, Vol.91 (3), p.922-926
• Main Authors: Madani, Nahid D., Malloy, Peter J., Rodriguez-Pombo, Pilar, Krishnan, Aruna V., Feldman, David
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Base Sequence; Biological and medical sciences; Biology; Candida albicans; Candida albicans - genetics; Candida albicans - metabolism; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell growth; Cloning, Molecular; DNA, Fungal - genetics; Enzymes; Estradiol - pharmacology; Estrogens; Estrogens - metabolism; Flavoproteins; Fundamental and applied biological sciences. Psychology; Fungi; Gels; Genes; Genes, Fungal; Growth, nutrition, metabolism, transports, enzymes. Molecular biology; Humans; Microbiology; Molecular Sequence Data; Mycology; NADPH Dehydrogenase - genetics; Oxidases; Oxidoreductases - antagonists & inhibitors; Oxidoreductases - genetics; Proteins; Receptors, Estrogen - genetics; Receptors, Estrogen - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Sequence Homology, Amino Acid; Steroids; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.3.922

Candida albicans, the most common fungal pathogen of humans, possesses an estrogen-binding protein (EBP) that binds mammalian estrogens with high affinity. We report here the cloning and complete nucleotide sequence of a gene encoding a C. albicans EBP. Amino acid sequences obtained from cyanogen bromide fragments of purified EBP were used to design oligonucleotide primers for PCR. An 800-bp product was amplified and used to screen a C. albicans genomic library. A clone was isolated containing an insert with an open reading frame of 1221 nt capable of encoding a protein with 407 amino acids and having a calculated molecular mass of 46,073 Da, the estimated size of EBP. The cloned gene, expressed in Escherichia coli as a lacZ fusion protein, demonstrated high-affinity binding for estradiol and a competition profile comparable to C. albicans wild-type EBP. Northern blots of C. albicans RNA revealed a single transcript of ≈1600 nt, whereas Southern blots identified three hybridizing fragments. Computer searches of data bases showed that EBP shares a 46% amino acid identity with the old yellow enzyme, an oxidoreductase from Saccharomyces cerevisiae, but was unrelated to the human estrogen receptor as previously speculated. In addition, a 51-amino acid region of EBP is highly conserved among a group of flavoproteins including old yellow enzyme. Expressed EBP was shown to exhibit oxidoreductase activity that could be inhibited by 17β-estradiol in vitro. In conclusion, the EBP from C. albicans has no evident homology to the mammalian steroid receptor superfamily but appears to be a member of a recently identified family of flavoproteins.