The targeted inactivation of polyketide synthase mycAV in the mycinamicin producer, Micromonospora griseorubida, and a complementation study.

Mycinamicin is a 16-membered macrolide antibiotic produced by Micromonospora griseorubida A11725, which shows strong antimicrobial activity against gram-positive bacteria. Recently, the nucleotide sequences of the mycinamicn biosynthetic gene cluster in M. griseorubida have been completely determined. Mycinamicin non-producer M7A21 was isolated by mycAV inactivation, which encodes the module 7 of mycinamicin polyketide synthase (PKS) required for the biosynthesis of the mycinamicin biosynthetic intermediate protomycinolide-IV (PML-IV). When the bioconversion to mycinamicin II (M-II) from PML-IV was performed using M7A21 and the feeding culture method, the productivity of M-II was the same as that of M-II in wild-type strain A11725. p446M7 containing mycAV was constructed using the Escherichia coli-Streptomyces shuttle vector pGM446. The mycinamicin productivity of M7A21 was restored by the introduction of p446M7 into the M7A21 cell, but almost all p446M7 was integrated into the chromosome of M7A21 because the plasmid was unstable in M7A21. The feeding culture and the introduction of the complement gene for M7A21 would be powerful tools to perform combinatorial biosynthesis for the production of new macrolide antibiotics.