New Ene Diyne Antitumor Antibiotic C-1027 Biosynthesis Research

C-1027, which is produced by Strptomyces globisporus C-1027, is a novel antitumor antibiotic composed of an acidic apoprotein non-covalently linked with a chromophore. The apoprotein contains 110 amino acid residues and the corresponding gene ( cagA) has been cloned and sequenced. The apoprotein acts as a stabilizer to maintain the unstable chromophore and make it soluble, and probably as a carrier to transfer the chromophore out of the cell because the cagA encodes the pre-apoprotein with a typical leader peptide of 32 amino acid residues. Thus, the apoprotein may function as a self-resistance role for the C-1027 producer as well to sequester the chromophore. On the other hand, the chromophore of C-1027 is responsible for the biological activity, containing two acetylenic groups conjugated to a double bond within a nine-member ring i.e. the enediyne core. The mechanism of action is that the enediyne core undergoes an electronic rearrangement to form a transient benzenoid diradical, which is positioned in the DNA minor groove to damage the target DNA by abstracting the hydrogen atoms from deoxyriboses on both strands. C-1027 is currently the most potent, highly antitumor agent in the enediyne family, which is 1000-fold higher than adriamycin, one of the most effective, clinically used antitumor antibiotics. The endiyne antibiotics are recently the focus of intense research activity in the field of chemistry, biology and medical science, because their unusual molecular architecture, phenomenal biological activity, and fascinating modes of action. The study of C-1027 will be useful for clarify the mechanism of enediyne antibiotic biosynthesis, and develope some novel, clinically used antitumor drugs by combinatoral biosynthesis.The C-1027 chromophore is proposed to be composed of four building blocks: the bensoxazolinate, the deoxy aminosugar, the p-amino acid and the enediyne core. First, the genomic library of S. globisporus C-1027 was developed with cosmid pOJ446 as vector. Using a set of primers designed accoding to the conserved sequence of dNDP-glucose dehydratase gene from various...