Biosynthesis And Bioactivities Of Jadomycin Derivatives

Jadomycins refer to a series of atypical angucycline antibiotics produced by Streptomyces venezuelae ISP5230 under nutrient limitation and environmental stresses, such as heat shock, ethanol treatment and phage infection. The key steps of the jadomycin biosynthesis are the oxidative opening of ring B in an angucyclinone intermediate, and the succeeding insertion of an amino acid molecule. By introducing different amino acids, a compound library can be formed.It is speculated that the incorporation of amino acids is nonenzymatical. By providing different amino acids in the culture medium,12 jadomycins with different sidechains at position C1 were identified. In order to increase the yields of jadomycins, the fermentation conditions were optimized by changing the strain and medium used in fermentation, and the strength and time of ethanol treatment.10 jadomycins were purified through column chromatography and HPLC, including 5 novel derivates:JdNle; JdAbu; JdDaba; JdO; JdHse.The anti-tumor activities of 7 derivates were tested. The growth of two human tumor cell lines MCF-7 (Human breast cancer cells) and HCT116 (Human colon cancer cells) were inhibited significantly by 4 jadomycins with alkyl sidechains, with IC50 ranging from 1.7 to 3.5μM. The in vitro and in vivo activities toward aurora kinase B/A were tested via Elisa and Western blot. At 10μM level, the in vitro inhibitions to aurora kinase B/A were all lower than 50%, while at 20μM level, no in vivo inhibitions were observed, suggesting that jadomycins may have other targets.JadH is an FAD-dependent bifunctional hydroxylase/dehydrase, catalysing 2,3-dehydro-UWM6 to dehydrorabelomycin. The structure model of JadH was constructed, and the key residues involved in substrate recognition, conformational switching and affecting the electrostatic property of substrate binding region were predicted through structure analysis and sequence comparison. A series of JadH mutants were obtained by site-derected mutations, expressed in E. coli BL21 and purified using Ni-NTA column. By comparing the relative activities of the mutants to that of wild-type JadH, the predictied key residues were identified.