Faculty of Pharmacy, Chiba Institute of Science, Shiomi-cho, Choshi, Chiba, Japan.
Amino Acids. 2014 Mar;46(3):661-70. doi: 10.1007/s00726-013-1517-x. Epub 2013 May 30.
Properties of putrescine uptake by PotFGHI and PuuP and their physiological significance were studied using a polyamine biosynthesis and uptake deficient Escherichia coli KK3131 transformed with pACYC184 containing potFGHI or puuP. Putrescine uptake activity of E. coli KK3131 transformed with pACYC184-PotFGHI was higher than that of E. coli 3131 transformed with pACYC-PuuP when cells were cultured in the absence of putrescine. Putrescine uptake by PotFGHI was both ATP and membrane potential dependent, while that by PuuP was membrane potential dependent. Feedback inhibition by polyamines occurred at the PotFGHI uptake system but not at the PuuP uptake system. Expression of PuuP was reduced in the presence of PuuR, a negative regulator for PuuP, and expression of PuuR was positively regulated by glucose, which reduces the level of cAMP. The complex of cAMP and CRP (cAMP receptor protein) inhibited the expression of PuuR in the absence of glucose. Thus, the growth rate of E. coli KK3131 in the presence of both 0.4% (22.2 mM) glucose and 10 mM putrescine was in the order of cells transformed with pACYC-PotFGHI > pACYC-PuuP > pACYC-PuuP + PuuR, which was parallel with the polyamine content in cells. The results indicate that PotFGHI is necessary for rapid cell growth in the presence of glucose as an energy source. When glucose in medium was depleted, however, PuuP was absolutely necessary for cell growth in the presence of putrescine, because accumulation of putrescine to a high level by PuuP was necessary for utilization of putrescine as an energy source.
腐胺摄取的特性由 PotFGHI 和 PuuP 及其生理意义进行了研究，使用多胺生物合成和摄取缺陷大肠杆菌 KK3131 转化为 pACYC184 含有 potFGHI 或 puuP。当细胞在没有腐胺的情况下培养时，转化为 pACYC184-PotFGHI 的大肠杆菌 KK3131 的腐胺摄取活性高于转化为 pACYC-PuuP 的大肠杆菌 3131。腐胺摄取由 PotFGHI 既依赖于 ATP 和膜电位，而由 PuuP 依赖于膜电位。多胺的反馈抑制发生在 PotFGHI 摄取系统，但不是在 PuuP 摄取系统。在 PuuR 的存在下，PuuP 的表达减少，PuuR 是 PuuP 的负调节因子，并且 PuuR 的表达受到葡萄糖的正调节，葡萄糖降低了 cAMP 的水平。cAMP 和 CRP（cAMP 受体蛋白）的复合物在没有葡萄糖的情况下抑制 PuuR 的表达。因此，在存在 0.4%（22.2mM）葡萄糖和 10mM 腐胺的情况下，大肠杆菌 KK3131 的生长速率的顺序为转化为 pACYC-PotFGHI 的细胞>转化为 pACYC-PuuP 的细胞>转化为 pACYC-PuuP+PuuR 的细胞，这与细胞中的多胺含量平行。结果表明，当葡萄糖作为能量源存在时，PotFGHI 是快速细胞生长所必需的。然而，当培养基中的葡萄糖耗尽时，PuuP 是在存在腐胺的情况下细胞生长所绝对必需的，因为通过 PuuP 将腐胺积累到高水平是将腐胺用作能源的必要条件。
