State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
Appl Microbiol Biotechnol. 2015 Apr;99(7):3141-53. doi: 10.1007/s00253-014-6368-1. Epub 2015 Jan 11.
Myo-inositol is important for Streptomyces growth and morphological differentiation. Genomic sequence analysis revealed a myo-inositol catabolic gene cluster in Streptomyces coelicolor. Disruption of the corresponding genes in this cluster abolished the bacterial growth on myo-inositol as a single carbon source. The transcriptions of these genes were remarkably enhanced by addition of myo-inositol in minimal medium. A putative regulatory gene SCO6974, encoding a GntR family protein, is situated in the cluster. Disruption of SCO6974 significantly enhanced the transcription of myo-inositol catabolic genes. SCO6974 was shown to interact with the promoter regions of myo-inositol catabolic genes using electrophoretic mobility shift assays. DNase I footprinting assays demonstrated that SCO6974 recognized a conserved palindromic sequence (A/T)TGT(A/C)N(G/T)(G/T)ACA(A/T). Base substitution of the conserved sequence completely abolished the binding of SCO6974 to the targets demonstrating that SCO6974 directly represses the transcriptions of myo-inositol catabolic genes. Furthermore, the disruption of SCO6974 was correlated with a reduced sporulation of S. coelicolor in mannitol soya flour medium and with the overproduction of actinorhodin and calcium-dependent antibiotic. The addition of myo-inositol suppressed the sporulation deficiency of the mutant, indicating that the effect could be related to a shortage in myo-inositol due to its enhanced catabolism in this strain. This enhanced myo-inositol catabolism likely yields dihydroxyacetone phosphate and acetyl-CoA that are indirect or direct precursors of the overproduced antibiotics.
肌醇对链霉菌的生长和形态分化很重要。基因组序列分析显示链霉菌中有肌醇分解代谢基因簇。该簇中相应基因的破坏使细菌无法以肌醇为单一碳源生长。在最小培养基中添加肌醇可显著增强这些基因的转录。一个假定的调节基因 SCO6974，编码 GntR 家族蛋白，位于该簇中。SCO6974 的破坏显著增强了肌醇分解代谢基因的转录。电泳迁移率变动分析表明，SCO6974 与肌醇分解代谢基因的启动子区相互作用。DNase I 足迹分析表明，SCO6974 识别保守的回文序列（A/T）TGT（A/C）N（G/T）（G/T）ACA（A/T）。保守序列的碱基替换完全消除了 SCO6974 与靶标的结合，证明 SCO6974 直接抑制肌醇分解代谢基因的转录。此外，SCO6974 的破坏与 S. coelicolor 在甘露醇大豆粉培养基中的孢子形成减少以及放线紫红素和钙依赖性抗生素的过度产生有关。添加肌醇抑制了突变体的孢子形成缺陷，表明这种影响可能与由于该菌株中肌醇代谢增强而导致的肌醇短缺有关。这种增强的肌醇分解代谢可能产生 1,3-二羟丙酮磷酸和乙酰辅酶 A，它们是过度产生的抗生素的间接或直接前体。
