An exo-beta-(1,3)-glucanase of Candida albicans: purification of the enzyme and molecular cloning of the gene.

A nucleotide sequence encoding an exo-beta-(1,3)-glucanase was cloned from a library of genomic DNA of Candida albicans ATCC 10261. The sequenced gene encodes a protein of 438 amino acid residues. The amino terminal and an internal peptide sequence of the enzyme matched with deduced sequences within the cloned gene. Analysis of the sequence indicated that the nascent protein is processed during secretion by the signal peptidase and a Kex2-like proteinase, yielding a predicted mature enzyme of 400 residues. There is 58% identity and 85% similarity between the amino acid sequences of this exoglucanase and the homologous enzyme of Saccharomyces cerevisiae. An antiserum to the purified exoglucanase cross-reacted with the S. cerevisiae exoglucanase and a similar protein secreted by other C. albicans strains and Candida species. There are no sites for N-linked glycosylation in the sequence and this is consistent with the carbohydrate content of the secreted enzyme. Putative upstream promoter elements are associated with the gene. Southern analysis of the gene indicated that it was present at one copy per genome and that the diploid genome of C. albicans ATCC 10261 is heterozygous at this locus for a BglII RFLP. A 2.5 kb mRNA transcript was detected by Northern analysis and gene expression, as monitored by Northern and Western blots, reflected the growth rates of the cultures.