Smirnova Galina V, Muzyka Nadezda G, Ushakov Vadim Y, Tyulenev Aleksey V, Oktyabrsky Oleg N
Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm 614081, Russia.
Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm 614081, Russia; Department of Chemistry and Biotechnology, Perm National Research Polytechnic University, Perm, Russia.
Res Microbiol. 2015 Oct;166(8):609-17. doi: 10.1016/j.resmic.2015.07.007. Epub 2015 Aug 6.
The aim of the study was to elucidate a possible relationship between transmembrane cycling of glutathione and changes in levels of external superoxide. Exposure of growing Escherichia coli to exogenous reactive oxygen species (ROS) generated by xanthine and xanthine oxidase (XO) stimulates reversible glutathione (GSH) efflux from the cells that is considerably lowered under phosphate starvation. This GSH efflux is prevented by exogenous SOD, partially inhibited by catalase, and is not dependent on the GSH exporter CydDC. The γ-glutamyl transpeptidase (GGT) deficiency completely prevents a return of GSH to the cytoplasm. In contrast to wild-type E. coli, mutants devoid of GGT and glutathione reductase (GOR) show enhanced accumulation of oxidized glutathione in the medium after exposure to xanthine and XO. Under these conditions, sodC, ggt and especially gshA mutants reveal more intensive and prolonged inhibition of growth than wild-type cells. Treatment with XO does not influence E. coli viability, but somewhat increases the number of cells with lost membrane potential. In summary, data obtained here indicate that transmembrane cycling of GSH may be involved in E. coli protection against extracellular ROS and may promote rapid growth recovery.
本研究的目的是阐明谷胱甘肽的跨膜循环与细胞外超氧化物水平变化之间的可能关系。将生长中的大肠杆菌暴露于由黄嘌呤和黄嘌呤氧化酶（XO）产生的外源性活性氧（ROS）中，会刺激细胞内谷胱甘肽（GSH）的可逆外流，而在磷酸盐饥饿条件下，这种外流会显著降低。外源性超氧化物歧化酶（SOD）可阻止这种GSH外流，过氧化氢酶可部分抑制其外流，且其不依赖于GSH输出蛋白CydDC。γ-谷氨酰转肽酶（GGT）缺陷完全阻止了GSH返回细胞质。与野生型大肠杆菌相比，缺乏GGT和谷胱甘肽还原酶（GOR）的突变体在暴露于黄嘌呤和XO后，培养基中氧化型谷胱甘肽的积累增加。在这些条件下，sodC、ggt尤其是gshA突变体比野生型细胞表现出更强烈和持久的生长抑制。用XO处理不影响大肠杆菌的活力，但会使膜电位丧失的细胞数量略有增加。总之，此处获得的数据表明，GSH的跨膜循环可能参与大肠杆菌对细胞外ROS的保护，并可能促进其快速恢复生长。
