Excretion and uptake of cadaverine by CadB and its physiological functions in Escherichia coli
Excretion and uptake of cadaverine by CadB and its physiological functions in Escherichia coli
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DOI：
10.1046/j.1365-2958.2003.03913.x
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发表时间：
2004-03-01
影响因子：
3.6
通讯作者：
Igarashi, K
中科院分区：
文献类型：
--
作者：
Soksawatmaekhin, W;Kuraishi, A;Igarashi, K
在大肠杆菌中研究了推定的尸胺转运蛋白CadB的功能。CadB既有依赖于质子动力的尸胺摄取活性，又有尸胺排泄活性，充当尸胺-赖氨酸反向转运蛋白。对尸胺摄取和排泄的Km值分别为20.8和303 μ M。CadB的尸胺摄取和尸胺-赖氨酸逆向转运蛋白活性在细胞中是功能性的。细胞生长的多胺需要的突变体刺激轻微的尸胺摄取活性在中性pH值和大大在酸性pH值的尸胺-赖氨酸逆向转运蛋白的活性。在酸性pH下，在赖氨酸的存在下诱导含有cadB和cadA的编码赖氨酸脱羧酶的操纵子。这导致了细胞外介质的中和，并使得可能产生CO2和尸胺和氨丙基尸胺，而不是腐胺和亚精胺。cadBA操纵子的诱导也产生了质子动力。当cadBA操纵子不被诱导时，编码诱导型鸟氨酸脱羧酶和腐胺-鸟氨酸反向转运蛋白的speF-potE操纵子的表达增加。结果表明，cadBA操纵子在酸性pH下的细胞调节中起重要作用。
The functions of the putative cadaverine transport protein CadB were studied in Escherichia coli. CadB had both cadaverine uptake activity, dependent on proton motive force, and cadaverine excretion activity, acting as a cadaverine-lysine antiporter. The Km values for uptake and excretion of cadaverine were 20.8 and 303 muM respectively. Both cadaverine uptake and cadaverine-lysine antiporter activities of CadB were functional in cells. Cell growth of a polyamine-requiring mutant was stimulated slightly at neutral pH by the cadaverine uptake activity and greatly at acidic pH by the cadaverine-lysine antiporter activity. At acidic pH, the operon containing cadB and cadA, encoding lysine decarboxylase, was induced in the presence of lysine. This caused neutralization of the extracellular medium and made possible the production of CO2 and cadaverine and aminopropylcadaverine instead of putrescine and spermidine. The induction of the cadBA operon also generated a proton motive force. When the cadBA operon was not induced, the expression of the speF-potE operon, encoding inducible ornithine decarboxylase and a putrescine-ornithine antiporter, was increased. The results indicate that the cadBA operon plays important roles in cellular regulation at acidic pH.