Functional Analysis Of Candida Albicans CaPTC6 And CaHXT5 Genes As Well As Sacchromycease Cerevisae ScATP16 Gene

Candida albicans is the importantly opportunitive fungal pathogen. The type 2C protein phosphatases are one group of serine/threonine protein phosphatases involved in the reversible protein phosphorylation. Glucose is the major source of energy in cells and involved in many cellular processes. To identify potential drug target genes in the most important human fungal pathogen C. albicans, we chose to study the functions of CaPTC6 and CaHXT5 genes.From the Candida genome database, we identified CaPTC6 and CaHXT5 gene sequences. CaPTC6 has an open reading frame (ORF) of 1299bp in length, which encodes a protein of 433 amino acids sharing 26.9% similarity with ScPtc6p at amino acid level. We cloned and expressed the catalytic domain of CaPtc6p, and found that the purified catalytic domain 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 that CaPTC6 encoded a PP2C phosphatase. We constructed the homozygous deletion mutant for CaPTC6, but did not find any phenotype for this mutant under various growth conditions.CaHXT5 has an ORF of 1836bp, which encodes a protein of 612 amino acids sharing 28% similarity with ScHxt5p at the amino acid level. We constructed the homozygous mutant of CaHXT5. However, the homozygous mutant did not show any visible phenotype in utilization of different sugars and in hypha formation. We speculate that other members of glucose transporters might play a redundant role for CaHxt5p in these processes.Recent studies show that the ScATP16-encodedδsubunit of the mitochondrial F1F0-ATP synthase is phosphorylated in Saccharomyces cerevisia. To understand the molecular mechanism by which the phosphorylation of the delta subunit is regulated. We expressed aδ-His6 fusion protein in bacterial cells and prepared its rabbit polyclonal antibodies. In addition, we applied site-directed mutagenesis to construct the point mutant at the phosphorylation site of theδsubunit. However, we found that this mutation does not affect the function of mitochondrial ATP synthase in the utilization of nonfermentable carbon sources.