Genomic-driven discovery of an amidinohydrolase involved in the biosynthesis of mediomycin A.

Clethramycin (1) and mediomycin A (2) belong to the linear polyene polyketide (LPP) family of antibiotics that exhibit potent antifungal activity. Structural similarities exist between 1 and 2, except that 2 contains an amino moiety substituted for the guanidino moiety. Herein, the draft genome sequence of Streptomyces mediocidicus ATCC23936, a strain which produces both 1 and 2, was obtained through de novo sequencing. Bioinformatic analysis of the genome revealed a clethramycin (cle) gene cluster that contained 25 open reading frames (orfs). However, amidinohydrolase for 2 formation was not found in the cle gene cluster. Further genomic analysis revealed an amidinohydrolase MedX, which can hydrolyse the guanidino form (1) into the amino form (2) via heterologous co-expression of the cle cluster in Streptomyces lividans or by in vitro catalysis. These results also suggest the feasibility of engineering novel LPPs for drug discovery by manipulating the biosynthetic machinery of S. mediocidicus.