The Candida albicans CHS4 gene complements a Saccharomyces cerevisiae skt5/chs4 mutation and is involved in chitin biosynthesis

The Candida albicans CHS4 gene encoding chitin synthase 4 has been isolated using the Saccharomyces cerevisiae CHS4/SKT5 gene as a probe. The gene contains a 2061 bp open reading frame capable of encoding a protein of 687 amino acids (76053 Da). No intron was observed in the gene. Disruption of CHS4 in C. albicans yielded a Calcofluor-resistant phenotype, indicating that Chs4p contributes to chitin biosynthesis. Consistent with this, overexpression of Chs4p under the regulation of the ScGAL1 promoter enhanced chitin synthase 3 activity in S. cerevisiae 7- to 38-fold. In addition, chs3 and chs4 null mutants were significantly defective in Calcofluor white staining and their chitin content was 10% of that of the parental strain. Chs4p of C. albicans and S. cerevisiae showed 61 % identity in the C-terminal half of the proteins and that region of C. albicans Chs4p complemented the Chs4p function of a mutant of S. cerevisiae resistant to Calcofluor white. Therefore, it appears that Chs4p is involved in chitin synthase 3 activity by combining with Chs3p to interact synergistically in chitin biosynthesis.