The biosynthetic gene cluster for the enediyne antitumor antibiotic neocarzinostatin (NCS) was localized to 130 kb continuous DNA from Streptomyces carzinostaticus ATCC15944 and confirmed by gene inactivation. DNA sequence analysis of 92 kb of the cloned region revealed 68 open reading frames (ORFs), 47 of which were determined to constitute the NCS cluster. Sequence analysis of the genes within the NCS cluster suggested dNDP-D-mannose as a precursor for the deoxy aminosugar, revealed two distinct type I polyketide synthases (PKSs), and supported a convergent model for NCS chromophore biosynthesis from the deoxy aminosugar, naphthoic acid, and enediyne core building blocks. These findings shed light into deoxysugar biosynthesis, further support the iterative type I PKS paradigm for enediyne core biosynthesis, and unveil a mechanism for microbial polycyclic aromatic polyketide biosynthesis by an iterative type I PKS.
Analysis of the genome of Streptomyces aizunensis NRRL B-11277 indicated its potential to produce a compound of novel and highly predictable structure. The structure was predicted with sufficient accuracy to allow straightforward detection of the specific metabolite in HPLC profiles of fermentation extracts and hence to guide the isolation. The spectroscopic work was reduced to a confirmation of structure rather than a first principle determination. The compound, ECO-02301 (1), demonstrated potent antifungal activity. This work exemplifies not only the discovery of novel antibiotics from well-characterized organisms but also the utility of genomics as a further tool, complementary to spectroscopy, to enable rapid determination of complex structures.
