Identification And Characterization Of Candida Albicans TCO89 And PTC1 Genes

Candida albicans is the most important fungal pathogen in humans. Recent studies on C. albicans have been focused on understanding its pathogenesis and on identifying therapeutic targets for the development of novel antifungal drugs. From Stanford C. albicans genomic database, we identified CaTCO89 and CaPTC1 gene sequences. CaTCO89 has an ORF of 2127 bp, which encodes a protein of 708 amino acids sharing 17% identity and 28% similarity with ScTco89p at the amino acids level. We found that CaTCO89 could complement the functions of ScTCO89 in rapamycin and lithium tolerance as well as in cellular integrity in S. cerevisiae. We constructed the deletion mutant of CaTCO89 (TJU4) in RM1000 background. In comparison with RM1000, TJU4 cells showed rapamycin and lethium sensitivity. Ectopic expression of CaTCO89 recovered the tolerance of TJU4 cells to rapamycin to the level of the wild-type RM1000 cells, but significantly increased the tolerance of TJU4 cells to LiCl and H2O2 and the sentivity to CdCl2 above the levels of RM1000 cells. Deletion of CaTCO89 did not affect the morphological development. However, ectopic expression of CaTCO89 caused cell aggregation of C. albicans in Spider and SD-Ura liquid medium as welll as formation of smooth and bread-shaped coloneys on solid spider medium.CaPTC1 has an ORF of 1128 bp in length, which encodes a protein of 375 amino acids sharing 41% identity and 52% similarity with ScPtc1p. We disrupted the two alleles of CaPTC1 from RM1000, which resulted in the strain SYY4. SYY4 cells showed sensitivity to LiCl, NaCl and KCl but not the osmolar agent sorbitol. Ectopic expression of CaPTC1 recovered the tolerance of SYY4 to these salt stresses. The DNA sequence encoding the catalytic domain of CaPtc1p was cloned and expressed in E. Coli cells. The purified protein exhibited dephosphorylation activity, which was dependent on the presence of Mg2+ or Mn2+ ion and inhibited by the protein Ser/Thr phosphatase inhibitor NaF. These results indicate CaPTC1 encodes a type 2C Ser/Thr phosphatase (PP2C).