Abstract
After screening a Candida albicans genome data base, the product of an open reading frame (IPF 19760/CA2574) with 41% identity to Saccharomyces cerevisiae vacuolar acid trehalase (Ath1p) was identified and named Atc1p. The deduced amino acid sequence shows that Atc1p contains an N-terminal hydrophobic signal peptide and 20 potential sites for N-glycosylation. C. albicans homozygous mutants that lack acid trehalase activity were constructed by gene disruption at the two ATC chromosomal alleles. Analysis of these null mutants shows that Atc1p is localized in the cell wall and is required for growth on trehalose as a carbon source. An Atc1p endowed with acid trehalase activity was obtained by an in vtro transcription-translation coupled system. These results strongly suggest that ATC1 is the structural gene encoding cell wall acid trehalase in C. albicans. Determinations of ATC1 mRNA expression as well as acid trehalase activity in the presence and absence of glucose point out that ATC1 gene is regulated by glucose repression.
Highlights
The non-reducing disaccharide trehalose (␣-D-glucopyranosil ␣-D-glucopyranoside) has been identified and characterized in a wide variety of organisms ranging from bacteria and fungi to plant and mammals [1,2,3]
C. albicans cells were grown in YP medium (1% yeast extract, 2% bactopeptone) [36] or MM medium (0.7% yeast nitrogen base without amino acids) supplemented with the appropriate nutrients in amounts specified by Sherman [36] and with the appropriate carbon source (2% glucose or 2% trehalose)
CA2574 shares 41% identical and 59% similar amino acids with Ath1p and 29% identical and 47% similar amino acids with TreAp, both comparisons being made over their entire length. These results suggest that IPF 19760 could encode C. albicans acid trehalase, for which reason we called it Atc1p
Summary
The non-reducing disaccharide trehalose (␣-D-glucopyranosil ␣-D-glucopyranoside) has been identified and characterized in a wide variety of organisms ranging from bacteria and fungi to plant and mammals [1,2,3]. In Saccharomyces cerevisiae and Candida utilis, both kinds of cytosolic and vacuolar trehalases are present [2, 3, 10] In fungi such as Neurospora crassa and Mucor rouxii, acid trehalase activity is linked to the cell wall of ascospores and conidiospores [19, 20]. Trehalose metabolism has been intensively investigated in C. albicans in connection with dimorphism and as a possible contributory factor to its virulence In this respect, disruption of TPS1 impairs hypha formation and decreases infectivity [30], whereas TPS2 is involved in cell integrity and pathogenicity but is not required for dimorphic transition [31, 32].
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