Cloning, sequence analysis and expression of the gene encoding imidazole glycerol phosphate dehydratase in Cryptococcus neoformans.

A cDNA from Cryptococcus neoformans, encoding imidazole glycerol phosphate dehydratase (IGPD), was isolated by complementation of a his3 mutant strain of Saccharomyces cerevisiae. The C. neoformans HIS3 cDNA encodes an approx. 22-kDa protein with a high degree of amino-acid sequence similarity to IGPDs from ten other microorganisms, as well as Arabidopsis thaliana. Most striking are two conserved HHXXE regions and several conserved His, Asp and Glu residues. The cDNA was engineered for expression in Escherichia coli and an approx. 26-kDa protein was identified by SDS-PAGE. DNA and N-terminal sequence analyses confirmed that this protein was C. neoformans IGPD. Furthermore, IGPD assays of crude extracts from IGPD-producing E. coli cells demonstrated that the C. neoformans protein was catalytically active.