酮基合酶AlpRQ影响醌那霉素的产量

Ketosynthetases AlpRQ affects the yield of kinamycin

【背景】角蒽环类聚酮化合物醌那霉素生物合成基因簇包含了两套酮基合酶(KS_(α)和KS_(β))的编码基因,即alpA,alpB和alpR,alpQ,AlpA和AlpB被证明是醌那霉素合成过程中必需的酮基合酶,而AlpR和AlpQ则被认为与别的化合物的合成相关。【目的】鉴于alpR和alpQ和必需基因alpS在醌那霉素合成基因簇上紧密相邻,本研究旨在确定它们与醌那霉素生物合成的相关性。【方法】PCR-targeting在细菌人工染色体(BAC)文库质粒上进行多基因敲除,构建好的文库质粒再导入通用宿主Streptomyces albus J1074中进行异源表达,并用高效液相色谱(HPLC)检测突变株和野生型菌株的发酵产物。【结果】AlpR和AlpQ对醌那霉素的合成没有直接影响,但是敲除AlpRQ突变株的发酵液中醌那霉素的产量显著提高了。【结论】AlpR和AlpQ很有可能是另一Ⅱ型聚酮化合物的KS_(α)和KS_(β),它们与AlpA和AlpB竞争共同的合成前体。本研究还证明了AlpR和AlpQ并不能替代AlpA和AlpB的功能。

Kinamycin gene cluster contains two ketosynthase(KS_(α)and KS_(β))coding genes,namely alpA,alpB and alpR,alpQ,the first two are necessary for the synthesis of kinamycin,and alpR and alpQ are thought to be involved in the synthesis of other compounds.[Objective]Since alpR and alpQ are adjacent to the essential gene alpS in the kinamycin synthesis gene cluster,this study aims to identify their correlation with kinamycin biosynthesis.[Methods]The PCR-targeting multigene knockout was done on the bacterial artificial chromosome library plasmid,and the constructed library plasmid was introduced into Streptomyces albus J1074,a general Streptomyces host.The fermentation products of the mutant and the wild-type strains were detected by high performance liquid chromatography.[Results]AlpR and AlpQ had no direct effect on the synthesis of kinamycin,but the yield of kinamycin increased significantly inΔalpRQ mutant.[Conclusion]AlpR and AlpQ are likely KS_(α)and KS_(β)for the biosynthesis of another type Ⅱ polyketide compound,competing for common synthetic precursors with AlpA and AlpB.This study also demonstrates that alpR and alpQ cannot complement the function of alpA and alpB.