Isolation and characterization of the GFA1 gene encoding the glutamine:fructose-6-phosphate amidotransferase of Candida albicans.
Glutamine:fructose-6-phosphate amidotransferase (glucosamine-6-phosphate synthase) catalyzes the first step of the hexosamine pathway required for the biosynthesis of cell wall precursors. The Candida albicans GFA1 gene was cloned by complementing a gfa1 mutation of Saccharomyces cerevisiae (previously known as gcn1-1; W. L. Whelan and C. E. Ballou, J. Bacteriol. 124:1545-1557, 1975). GFA1 encodes a predicted protein of 713 amino acids and is homologous to the corresponding gene from S. cerevisiae (72% identity at the nucleotide sequence level) as well as to the genes encoding glucosamine-6-phosphate synthases in bacteria and vertebrates. In cell extracts, the C. albicans enzyme was 4-fold more sensitive than the S. cerevisiae enzyme to UDP-N-acetylglucosamine (an inhibitor of the mammalian enzyme) and 2.5-fold more sensitive to N3-(4-methoxyfumaroyl)-L-2,3-diaminopropanoic acid (a glutamine analog and specific inhibitor of glucosamine-6-phosphate synthase). Cell extracts from the S. cerevisiae gfa1 strain transformed with the C. albicans GFA1 gene exhibited sensitivities to glucosamine-6-phosphate synthase inhibitors that were similar to those shown by the C. albicans enzyme. Southern hybridization indicated that a single GFA1 locus exists in the C. albicans genome. Quantitative Northern (RNA) analysis showed that the expression of GFA1 in C. albicans is regulated during growth: maximum mRNA levels were detected during early log phase. GFA1 mRNA levels increased following induction of the yeast-to-hyphal-form transition, but this was a response to fresh medium rather than to the morphological change.
Smith
R J
RJ
Molecular & Cell Biology, Marischal College, University of Aberdeen, United Kingdom.
Milewski
S
S
Brown
A J
AJ
Gooday
G W
GW
D000595:Amino Acid Sequence; D001483:Base Sequence; D002176:Candida albicans / Q000166:cytology / Q000201:enzymology / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing) / Q000235:genetics*; D008969:Molecular Sequence Data; D009024:Morphogenesis; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014170:Transformation, Genetic
D005656:Fungal Proteins; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing)