Nucleotide Sequence of Conjugative and Integrating Plasmid pSLS from Streptomyces laurentii ATCC31255

The complete nucleotode sequence of a conjugative and inttegrative plasmid, pSLS, in the thiostrepton-production Streptomyces laurentii ATCC31255 was determined. The circular DNA molecule was 15,398 bp in length and contained 70.8% G+C content. Computer-assisted analysis indicated that pSLS contained 10 open reading frames (ORFs), orf1 to orf10, located on both strands of pSLS. The orf1 encoded for a predicted protein (200 aa) showed high similality to TraA protein of non-integrative plasmid pJV1 in Streptomyces involved in plasmid transfer and pock-formation. The orf2 coded for a protein of 660 aa that shared homology with TraB proteins encoded by other Streptomyces proteins, SpdBl, SpdB2 and SpdB3, respectively, which were also ivolved in plasmid spreading. The orf8 encoded a polypeptide of 458 aa that shared homology with Int protein of integrative plasmid pSAM2 in Streptomyces ambofacience. This report manifests that pSLS is unique chemeric episomal element that contains gene cluster from non-integrative plasmid and genes for site-specific integration from integrative plasmid