Streptomyces produces macrolide antibiotics. Macrolides are widely used in human and animal therapeutics and inhibit protein synthesis by a mechanism involving the binding of the antibiotic to the large subunit of the ribosome.
The integrative element pSAM2 from S ambofaciens was characterized using genetic and molecular biology.The genes involved in the site specific integration and excision in the transfer, kill-kor and in replecation were identified. pSAM2 integrate site specifically in the genome of many Streptomyces and some actimonomycetes through an attachment site present both on the element (attP) and on the chromosome (attB). attB overlaps the 3' ned of a tRNA gene.
Integrative vectors derived from pSAM2 have been constructed. They do not need any selective pressure to be maintained and they have a wide host range amongst actinomycetes. The gene pra (pSAM2 replication activation) involved in the positive regulation of replication during ttransfer have been characterized.
Two genes conferring resistance by ribosomal modification (23S rRna methylation) have been characterized. A gene whose product inactivates some macrolides by glycosylation and a gene supposed to be involved in antibiotic export are also present in S ambofaciens. A fifth resistance gene has not been characterized yet.
Two genes have been identified in S lividans: arepressor of the LacI type having pleiotropic effects on the expression of amylases, chitinases and xylanases, and a gene showing sequences homologies with inositol mono-phosphatases.