SEQUENCE-ANALYSIS OF THE CANDIDA-ALBICANS ADE2 GENE AND PHYSICAL SEPARATION OF THE 2 FUNCTIONALLY DISTINCT DOMAINS OF THE PHOSPHORIBOSYLAMINOIMIDAZOLE CARBOXYLASE

An ADE2 genomic clone from the pathogenic fungus, Candida albicans, wa s isolated by complementation of an Escherichia coil purK mutant and t he gene was analysed by DNA sequencing. A 1707 bp open reading frame w as identified encoding a polypeptide of 569 amino acids with significa nt homology to all the known yeast ADE2 genes. Sequence homology to bo th the E. coli purE and purK genes suggests that the C. albicans ADE2 gene is the result of an evolutionary fusion. The amino-acid sequence comparison showed that the N-terminal domain of the Ade2 protein has a 52.5% identity to PurK, whereas the C-terminal domain has a distinct 64.3% identity to PurE. In order to establish the functional relations hip of these two regions, deletion mutants of the Ade2 protein were pr epared by recombinant expression of the functional domains, which were tested by complementation of their respective E. coli auxotrophs. The sequence described in this paper has been deposited in the EMBL data library under the Accession Number U69606. (C) 1997 by John Wiley & So ns, Ltd.