Discovery of Venturicidin Congeners and Identification of the Biosynthetic Gene Cluster from sp. NRRL S-4.

Chemical screening of sp. NRRL S-4 with liquid chromatography-mass spectrometry (LC-MS) and the following chromatographic isolation led to the discovery of four 20-membered macrolides, venturicidin A () and three new congeners venturicidins D-F (-). Genome sequencing of strain S-4 revealed the presence of a biosynthetic gene cluster (BGC) encoding glycosylated type I polyketides (PKS). The BGC designated to venturicidin biosynthesis () was supported by the proposed biosynthetic pathway and confirmed by inactivation of the core PKS gene of . Bioinformatic analyses on the conserved motifs and known stereospecificities in PKS modules are consistent with the structure and absolute configuration. This is the first report of venturicidin BGC since the discovery of the macrolide in 1961. In the biological assays, venturicidin A () and E () displayed a high selective cytotoxicity against acute monocytic leukemia MV-4-11 cells with IC values of 0.09 and 0.94 μM, respectively. Venturicidin A () also showed a weak inhibitory activity on FMS-like-tyrosine kinase.