科研之友
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摘要
Background: Regulatory genes play critical roles in natural product biosynthetic pathways. Chromomycins are promising anticancer natural products from actinomycetes. This study is aimed to create an efficient strain for production of these molecules by manipulating the regulatory genes. @@@ Results: A putative but silent chromomycin biosynthetic gene cluster was discovered in Streptomyces reseiscleroticus. Heterologous expression of the ketosynthase, chain length factor, and acyl carrier protein in Streptomyces lividans confirmed that they are responsible for the assembly of a decaketide. Two regulatory genes are present in this gene cluster, including SARP-type activator SrcmRI and PadR-like repressor SrcmRII. Either overexpression of SrcmRI or disruption of SrcmRII turned on the biosynthetic pathway of chromomycins. The production titers of chromomycin A(3)/A(2) in R5 agar in these two strains reached 8.9 +/- 1.2/13.2 +/- 1.6 and 49.3 +/- 4.3/53.3 +/- 3.6 mg/L, respectively. An engineered strain was then constructed with both SrcmRII disruption and SrcmRI overexpression, which produced chromomycins A(3) and A(2) in R5 agar at 69.4 +/- 7.6 and 81.7 +/- 7.2 mg/L, respectively. Optimization of the culture conditions further increased the titers of chromomycins A(3) and A(2) respectively to 145.1 +/- 15.3 and 158.3 +/- 15.4 mg/L in liquid fermentation. @@@ Conclusions: This work revealed the synergistic effect of manipulation of pathway repressor and activator genes in the engineering of a natural product biosynthetic pathway. The resulting engineered strain showed the highest production titers of chromomycins by a strain of Streptomyces, providing an efficient way to produce these pharmaceutically valuable molecules.
- 出版日期2018-6-7
- 单位湖南中医药大学
