Molecular cloning and identification of the laspartomycin biosynthetic gene cluster from Streptomyces viridochromogenes

The biosynthetic gene cluster for laspartomycins, a family of 11 amino acid peptide antibiotics, has been cloned and sequenced from Streptomyces viridochromogenes ATCC 29814. Annotation of a segment of 88912 bp of S. viridochromogenes genomic sequence revealed the putative lpm cluster and its flanking regions which harbor 43 open reading frames. The lpm cluster, which spans approximately 60 kb, consists of 21 open reading frames. Those include four NRPS genes (lpmA/orf18, lpmB/orf25, lpmC/orf26 and lpmD/orf27), four genes (orfs 21, 22, 24 and 29) involved in the lipid tail biosynthesis and attachment, four regulatory genes (orfs 13, 19, 32 and 33) and three putative exporters or self-resistance genes (orfs 14, 20 and 30). In addition, the gene involved in the biosynthesis of the nonproteinogenic amino acid Pip was also identified in the lpm cluster while the genes necessary for the biosynthesis of the rare residue diaminopropionic acid (Dap) were found to reside elsewhere on the chromosome. Interestingly, the dabA, dabB and dabC genes predicted to code for the biosynthesis of the unusual amino acid diaminobutyric acid (Dab) are organized into the lpm cluster even though the Dab residue was not found in the laspartomycins. Disruption of the NRPS lpmC gene completely abolished laspartomycin production in the corresponding mutant strain. These findings will allow molecular engineering and combinatorial biosynthesis approaches to expand the structural diversity of the amphomycin-group peptide antibiotics including the laspartomycins and friulimicins.