Division of Applied Biology, Kyoto Institute of Technology, Kyoto, Japan.
Education and Research Center for Fermentation Studies, Faculty of Agriculture, Kagoshima University, Kagoshima, Japan.
Biosci Biotechnol Biochem. 2021 Mar 24;85(4):981-988. doi: 10.1093/bbb/zbaa109.
Escherichia coli strain, whose gene is one of the subunits of succinate dehydrogenase (sdhA), and gene of the transcriptional repressor of isocitrate lyase (iclR) were disrupted, accumulated 6.6 times as much intracellular succinate as the wild-type MG1655 strain in aerobic growth, but succinate was not found in the culture medium. E. coli citT gene that encodes a citrate transporter was cloned under the control of the lacI promoter in pBR322-based plasmid and the above strain was transformed. This transformant, grown under aerobic condition in M9-tryptone medium with citrate, accumulated succinate in the medium while no succinate was found in the medium without citrate. CitT was active as a succinate transporter for 168 h by changing the culture medium or for 24 h in fed-batch culture. This study suggests that the CitT transporter functions as a succinate exporter in E. coli for succinate production in the presence of citrate.
大肠杆菌菌株，其基因是琥珀酸脱氢酶（sdhA）的亚基之一，异柠檬酸裂解酶（iclR）的转录抑制剂基因被破坏，在需氧生长中积累的细胞内琥珀酸比野生型 MG1655 菌株多 6.6 倍，但在培养基中未发现琥珀酸。在 pBR322 质粒上，柠檬酸转运蛋白（citT）基因在 lacI 启动子的控制下被克隆，上述菌株被转化。在含有柠檬酸的 M9-胰蛋白胨培养基中，在需氧条件下生长的转化体在培养基中积累琥珀酸，而在没有柠檬酸的培养基中则没有发现琥珀酸。通过改变培养基或在补料分批培养 24 小时，CitT 可作为琥珀酸转运蛋白持续 168 小时发挥作用。本研究表明，CitT 转运蛋白在大肠杆菌中作为琥珀酸的外排转运蛋白，在存在柠檬酸的情况下促进琥珀酸的产生。
