Molecular cloning and characterization of a glucan synthase gene from the human pathogenic fungus Paracoccidioides brasiliensis

1,3-beta-D-glucan is a fungal cell wall polymer synthesized by the multi-su bunit enzyme 1,3-beta-D-glucan synthase. A subunit of this integral membran e protein was first described as the product of the FKS1 gene from Saccharo myces cerevisiae using echinocandin mutants. Other FKS1 genes were also rep orted for Candida albicans, Aspergillus nidulans and Cryptococcus neoforman s. Here, we report the nucleotide sequence of the first homologous FKS gene cloned from the pathogenic fungus Paracoccidioides brasiliensis. An open r eading frame of 5942 bp was identified in the complete sequence, interrupte d by two putative introns, the first close to the 5' end and the second clo se to the 3' end of the gene. A promoter region is also described containin g consensus sequences such as canonical TATA and CAAT boxes and, possibly, multiple sites for glucose regulation by creA protein. The deduced sequence of 1926 amino acid show more than 85% similarity to FksAp from A. nidulans , and 71% to Fks1p and Fks2p from S. cerevisiae. Computational analysis of P. brasiliensis Fks1p suggests a similar structure to transmembrane protein s, such as FksAp, with the presence of two domains composed by hydrophobic helices that limit the putative highly hydrophilic catalytic domain within the cytoplasm. The complete nucleotide sequence of PbFKS1 and its flanking regions have been submitted to GenBank under Accession No. AF148715. Copyri ght (C) 2000 John Wiley & Sons, Ltd.