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J. Bacteriol., Apr 1996, 2320-2327, Vol 178, No. 8
RJ Smith, S Milewski, AJ Brown and GW Gooday
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.
Copyright © 1996, American Society for Microbiology
Isolation and characterization of the GFA1 gene encoding the glutamine:fructose-6-phosphate amidotransferase of Candida albicans
Molecular & Cell Biology, Marischal College, University of Aberdeen, United Kingdom.
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