Cloning, characterization and heterologous expression of a polyketide synthase and P-450 oxidase involved in the biosynthesis of the antibiotic oleandomycin

The gene cluster encoding the deoxyoleandolide polyketide synthase (OlePKS) was isolated from the oleandomycin producing strain Streptomyces antibioti cus. Sequencing of the first two genes encoding OlePKS, together with the p reviously identified third gene revealed an overall genetic and protein arc hitecture similar to that of the erythromycin gene cluster encoding the 6-d eoxyerythronolide B synthase (DEBS) from Saccharopolyspora erythraea. When the entire OlePKS (10,487 amino acids) was expressed in the heterologous ho st Streptomyces lividans, it produced 8,8a-deoxyoleandolide, an aglycone pr ecursor of oleandomycin. The role of the P-450 monooxygenase, OleP, in olea ndomycin biosynthesis was also examined in vivo by co-expression with DEBS in S. lividans. The production of 8,8a-dihydroxy-6-deoxyerythronolide B and other derivatives indicates that OleP is involved in the epoxidation pathw ay of oleandomycin biosynthesis. Since there are currently no genetic syste ms available for manipulation of the natural oleandomycin producing strain, the heterologous expression system reported here provides a useful tool fo r studying this important macrolide antibiotic.