Identification and reconstitution of the polyketide synthases responsible for biosynthesis of the anti-malarial agent, cladosporin

The anti-malarial agent cladosporin is a nanomolar inhibitor of Plasmodium falciparum lysyl-tRNA synthetase, and exhibits activity against both blood and liver stage infection. Cladosporin can be isolated from the fungus Cladosporium cladosporioides , where it was believed to be biosynthesized by a highly reducing (HR) and non-reducing (NR) iterative type I polyketide synthase (PKS) pair. Genome sequencing of the host organism, and subsequent heterologous expression of these enzymes in Saccharomyces cerevisiae produced cladosporin, confirming the identity of the putative gene cluster. Incorporation of a pentaketide intermediate analog indicated a 5+3 assembly by the HR PKS Cla2 and the NR PKS Cla3 during cladosporin biosynthesis. A putative lysyl-tRNA synthetase resistance gene was also identified in the cladosporin gene cluster. Analysis of the active site emphasizes key structural features thought to be important in resistance to cladosporin.