ISOLATION AND CHARACTERIZATION OF 2 CHITINASE-ENCODING GENES (CTS1, CTS2) FROM THE FUNGUS COCCIDIOIDES-IMMITIS

Two chitinase(CTS)-encoding genes (cts) from Coccidioides immitis (Ci) , a respiratory fungal pathogen of humans, were cloned and sequenced, Both the genomic and cDNA sequences are presented. The transcription s tart points and poly(A)-addition sites were confirmed. The cts1 gene c ontains five introns and a 1281-bp ORF which translates a 427-amino-ac id (aa) protein of 47.4 kDa. The cts2 gene contains two introns and a 2580-bp ORF which translates a 860-aa protein of 91.4 kDa, The deduced CTS1 protein showed highest homology to the Aphanocladium album and T richoderma harzianum CTS (74% and 76%, respectively), while CTS2 showe d highest homology to the CTS of Saccharomyces cerevisiae (Sc) and Can dida albicans (47% and 51%, respectively). The putative N-terminal seq uence of the mature CTS1 protein also showed 89% homology to the repor ted N-terminal sequence of a 48-kDa complement fixation antigen (CF-Ag ) of Ci which has demonstrated chitinase activity. The CF-Ag is a clin ically important antigen used in serodiagnosis of this fungal disease. CTS2 showed several of the conserved features of the Sc CTS, includin g putative catalytic and Ser/Thr-rich domains, and a C-terminal Cys-ri ch region. We propose that CTS1 and CTS2 of Ci are members of two dist inct classes of fungal chitinases, an observation not previously repor ted for a single fungus.