Discovery of the Streptoketides by Direct Cloning and Rapid Heterologous Expression of a Cryptic PKS II Gene Cluster from Streptomyces sp. Tü6314

Genome sequencing and bioinformatic analysis have identified numerous cryptic gene clusters that have the potential to produce novel natural products. Within this work, we identified a cryptic type II PKS gene cluster (skt) from Streptomyces sp. Tu6314. Facilitated by linear plus linear homologous recombination-mediated recombineering (LLHR), we directly cloned the skt gene cluster using the Streptomyces site-specific integration vector pSET152. The direct cloning allowed for rapid heterologous expression in Streptomyces coelicolor, leading to the identification and structural characterization of six polyketides (three known compounds and the new streptoketides), four of which exhibiting anti-HIV activities. Our study shows that the pSET152 vector can be directly used for LLHR, expanding the Rec/ET direct cloning toolbox and providing the possibility for rapid heterologous expression of gene clusters from Streptomyces.