CLONING, SEQUENCE-ANALYSIS AND EXPRESSION OF THE GENE ENCODING IMIDAZOLE GLYCEROL PHOSPHATE DEHYDRATASE IN CRYPTOCOCCUS-NEOFORMANS

A cDNA from Cryptococcus neoformans, encoding imidazole glycerol phosp hate dehydratase (IGPD), was isolated by complementation of a his3 mut ant strain of Saccharomyces cerevisiae. The C. neoformans HIS3 cDNA en codes an approx. 22-kDa protein with a high degree of amino-acid seque nce similarity to IGPDs from ten other microorganisms, as well as Arab idopsis thaliana. Most striking are two conserved HHXXE regions and se veral conserved His, Asp and Glu residues. The cDNA was engineered for expression in Escherichia coli and an approx. 26-kDa protein was iden tified by SDS-PAGE. DNA and N-terminal sequence analyses confirmed tha t this protein was C. neoformans IGPD. Furthermore, IGPD assays of cru de extracts from IGPD-producing E. coli cells demonstrated that the C. neoformans protein was catalytically active.