Isolation of the CHS4 gene of Paracoccidioides brasiliensis and its accommodation in a new class of chitin synthases

The nucleotide sequence of a chitin synthase gene (PbrCHS4) of the dimorphic fungal human pathogen Paracoccidioides brasiliensis has been determined. A homology search with the deduced amino acid sequence of PbrChs4 (1744 aa) reveals the presence of two distinct domains, an N-terminal domain showing up to 30% homology to myosin motor-like domains and a C-terminal domain with up to 68% homology to chitin synthases, as has been reported for some class V chitin synthases. However, unlike class V chitin synthases with myosin motor-like domains, PbrChs4 does not present characteristic signatures of myosin motor-like domains. Also, although the Chs domain presents the closest homology to other fungal class V enzymes, it is low enough to consider PbrChs4 as belonging to a new class, which we propose as class VII.