Nyström T, Larsson C, Gustafsson L
Department of General and Marine Microbiology, Lundberg Laboratory, Göteborg University, Sweden.
EMBO J. 1996 Jul 1;15(13):3219-28.
Using two-dimensional gel electrophoresis and N-terminal amino acid sequencing analysis, we demonstrate that a mutant of the global regulatory protein ArcA fails to decrease the synthesis of the TCA cycle enzymes malate dehydrogenase, isocitrate dehydrogenase, lipoamide dehydrogenase E3 and succinate dehydrogenase in response to stasis, while the increased production of the glycolysis enzymes phosphoglycerate mutase and pyruvate kinase is unaffected. Microcalorimetric and respiratory measurements show that the continued production of TCA cycle enzymes in the (delta)arcA mutant is manifested as an elevated rate of respiration and total metabolic activity during starvation. The (delta)arcA mutant is severely impaired in surviving prolonged periods of exogenous carbon starvation, a phenotype that can be alleviated by overproducing the superoxide dismutase SodA. In addition, flow cytometry demonstrates that starving (delta)arcA mutant cells, in contrast to wild-type cells, fail to perform reductive division, remain large and contain multiple chromosomal copies. We suggest that the ArcA-dependent reduced production of electron donors and the decreased level and activity of the aerobic respiratory apparatus during growth arrest is an integral part of a defense system aimed at avoiding the damaging effects of oxygen radicals and controlling the rate of utilization of endogenous reserves.
通过二维凝胶电泳和N端氨基酸测序分析，我们证明全局调节蛋白ArcA的一个突变体在静止状态下不能降低三羧酸循环酶苹果酸脱氢酶、异柠檬酸脱氢酶、硫辛酰胺脱氢酶E3和琥珀酸脱氢酶的合成，而糖酵解酶磷酸甘油酸变位酶和丙酮酸激酶产量的增加则不受影响。微量热法和呼吸测量表明，在（delta）arcA突变体中三羧酸循环酶的持续产生表现为饥饿期间呼吸速率和总代谢活性的升高。（delta）arcA突变体在长时间外源碳饥饿下存活能力严重受损，这种表型可通过超量表达超氧化物歧化酶SodA得到缓解。此外，流式细胞术表明，与野生型细胞相比，饥饿的（delta）arcA突变体细胞不能进行减数分裂，细胞体积仍然很大且含有多个染色体拷贝。我们认为，在生长停滞期间，ArcA依赖的电子供体产量降低以及好氧呼吸装置水平和活性的下降是防御系统的一个组成部分，旨在避免氧自由基的破坏作用并控制内源性储备的利用速率。
