The biosynthetic gene cluster for the antitumor drug bleomycin from Streptomyces verticillus ATCC15003 supporting functional interactions between nonribosomal peptide synthetases and a polyketide synthase.
BACKGROUND
The structural and catalytic similarities between modular nonribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs) inspired us to search for a hybrid NRPS-PKS system. The antitumor drug bleomycin (BLM) is a natural hybrid peptide-polyketide metabolite, the biosynthesis of which provides an excellent opportunity to investigate intermodular communication between NRPS and PKS modules. Here, we report the cloning, sequencing, and characterization of the BLM biosynthetic gene cluster from Streptomyces verticillus ATCC15003.


RESULTS
A set of 30 genes clustered with the previously characterized blmAB resistance genes were defined by sequencing a 85-kb contiguous region of DNA from S. verticillus ATCC15003. The sequenced gene cluster consists of 10 NRPS genes encoding nine NRPS modules, a PKS gene encoding one PKS module, five sugar biosynthesis genes, as well as genes encoding other biosynthesis, resistance, and regulatory proteins. The substrate specificities of individual NRPS and PKS modules were predicted based on sequence analysis, and the amino acid specificities of two NRPS modules were confirmed biochemically in vitro. The involvement of the cloned genes in BLM biosynthesis was demonstrated by bioconversion of the BLM aglycones into BLMs in Streptomyces lividans expressing a part of the gene cluster.


CONCLUSIONS
The blm gene cluster is characterized by a hybrid NRPS-PKS system, supporting the wisdom of combining individual NRPS and PKS modules for combinatorial biosynthesis. The availability of the blm gene cluster has set the stage for engineering novel BLM analogs by genetic manipulation of genes governing BLM biosynthesis and for investigating the molecular basis for intermodular communication between NRPS and PKS in the biosynthesis of hybrid peptide-polyketide metabolites.
Du
L
L
Department of Chemistry, University of California, Davis 95616, USA.
Sánchez
C
C
Chen
M
M
Edwards
D J
DJ
Shen
B
B
D000595:Amino Acid Sequence; D000903:Antibiotics, Antineoplastic / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D001761:Bleomycin / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D003001:Cloning, Molecular; D017124:Conserved Sequence; D005798:Genes, Bacterial / Q000235:genetics; D008956:Models, Chemical; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D005810:Multigene Family / Q000235:genetics*; D009844:Oligosaccharides / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D016366:Open Reading Frames / Q000235:genetics; D010453:Peptide Synthases / Q000235:genetics / Q000378:metabolism*; D015183:Restriction Mapping; D016415:Sequence Alignment; D013302:Streptomyces / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D013379:Substrate Specificity
D000903:Antibiotics, Antineoplastic; D009097:Multienzyme Complexes; D009844:Oligosaccharides; D001761:Bleomycin; D010453:Peptide Synthases