Tkachenko A G, Salakhetdinova O Ia, Pshenichnov M R
Mikrobiologiia. 1996 Nov-Dec;65(6):740-4.
Ammonium depletion in the nutrient medium induced an active transport of putrescine into the cell, which was not associated with its utilization as a nitrogen source. The uptake of putrescine was accompanied by a proportional release of potassium from the cells. Quantitative analysis of free as well as weakly and tightly bound pools of putrescine showed that this diamine was bound mainly to DNA. Topological studies by the plasmid method indicated an increase in the DNA supercoiling in response to the putrescine transport. In vitro experiments made it possible to establish an ambiguous dependence of DNA topology on putrescine content--its physiological concentrations (0.5-1.0 mM) enhanced DNA supercoiling, while higher concentrations (2-10 mM) caused gradual relaxation of DNA. A possible physiological significance of these effects in adaptive response of cells to ammonium deficiency is discussed.
营养培养基中铵的消耗诱导腐胺主动转运进入细胞，这与其作为氮源的利用无关。腐胺的摄取伴随着细胞中钾的成比例释放。对游离以及弱结合和强结合的腐胺池进行定量分析表明，这种二胺主要与DNA结合。通过质粒法进行的拓扑学研究表明，响应腐胺转运，DNA超螺旋增加。体外实验使得确定DNA拓扑结构对腐胺含量的模糊依赖性成为可能——其生理浓度（0.5 - 1.0 mM）增强了DNA超螺旋，而较高浓度（2 - 10 mM）导致DNA逐渐松弛。讨论了这些效应在细胞对铵缺乏的适应性反应中的可能生理意义。
