Establishment of a Host-Vector System for Micromonospora griseorubida and Characterization of Mycinamicin Biosynthetic Genes.

Mycinamicin is a 16-membered macrolide antibiotic produced by a “rare” actinomycete, Micromonospora griseorubida. Conditions for protoplasting of the mycelium of mycinamicin-producing M. griseorubida and regeneration of the protoplasts were established. A Micromonospora-E. coli shuttle cosmid vector, which was constructed from a cryptic plasmid of M. griseorubida and E. coli cosmid pJB8, was useful for manipulation of a long DNA sequence. The host vector system established in this way allowed to identify a gene (mycG) encoding a P-450-like protein probably responsible for both steps of hydroxylation and epoxidization of the lactone ring of mycinamicin. The mycG gene was located near myrB encoding a 23S rRNA methyltransferase as a self-resistance determinant and mycF encoding mycinamicin III O-methyltransferase. These studies will help to improve the mycinamicin productivity and to modify mycinamicin by genetic approaches.