pH and monovalent cations regulate cytosolic free Ca(2+) in E. coli.
pH and monovalent cations regulate cytosolic free Ca(2+) in E. coli.
复制标题
pH 和单价阳离子调节大肠杆菌中的胞质游离 Ca(2)。
DOI：
10.1016/j.bbamem.2008.02.006
复制
发表时间：
2008
期刊：
影响因子：
--
通讯作者：
A. Campbell
中科院分区：
文献类型：
--
作者：
R. Naseem;I. Holland;A. Jacq;K. Wann;A. Campbell
实验结果首次表明，pH和一价阳离子对大肠杆菌胞内游离Ca ~（2+）具有调节作用。通过Ca 2+流入和流出，使用水母发光蛋白监测大肠杆菌。在pH 7.5时，静息细胞溶质游离Ca 2+为0.2-0.5 µM。在碱性pH下，存在外部Ca 2+（1 mM）时，其升高至4 µM，在酸性pH下降低至0.9 µM。在50- 100 nM s−1下，去除外部Ca 2+导致细胞溶质游离Ca 2+立即降低。在pH 5.5、7.5和9.5时，外排率相同。因此，ChaA，一个假定的Ca 2 +/H+交换，似乎不是一个主要的Ca 2+流出途径。在不添加Na+但存在1 mM外部Ca 2+的情况下，胞质游离Ca 2+升高至约10 µM。加入Na+（半最大60 mM）在很大程度上阻止了这种增加，并立即刺激Ca 2+外流。然而，这种效果是不具体的，因为K+也刺激流出。与此相反，增加渗透压的蔗糖没有显着刺激Ca 2+外流。结果与H+和一价阳离子与Ca 2+竞争非选择性离子流入通道一致。在chaA和yrbG基因敲除中的Ca 2+进入和流出与野生型没有显著差异，证实了ChaA和YrbG似乎都没有在大肠杆菌中调节胞质Ca 2+中发挥主要作用。根据条件，计算出每秒每个细胞移动的Ca 2+离子的数量范围为<1至100。然而，电导率为100 pS的单个真核生物Ca 2+通道应每秒传导> 600万个离子。这就提出了关于细菌和其他小生命系统（如线粒体）中Ca 2+转运的性质和调节的基本问题，需要一种新的数学方法来描述这种离子运动。这一结果对E.大肠杆菌对不同的离子环境，如肠道，淡水和海水附近的污水流出物。
The results here show for the first time that pH and monovalent cations can regulate cytosolic free Ca2+in E. coli through Ca2+influx and efflux, monitored using aequorin. At pH 7.5 the resting cytosolic free Ca2+was 0.2–0.5 µM. In the presence of external Ca2+(1 mM) at alkaline pH this rose to 4 µM, being reduced to 0.9 µM at acid pH. Removal of external Ca2+caused an immediate decrease in cytosolic free Ca2+at 50–100nM s−1. Efflux rates were the same at pH 5.5, 7.5 and 9.5. Thus, ChaA, a putative Ca2+/H+exchanger, appeared not to be a major Ca2+-efflux pathway. In the absence of added Na+, but with 1 mM external Ca2+, cytosolic free Ca2+rose to approximately 10 µM. The addition of Na+(half maximum 60 mM) largely blocked this increase and immediately stimulated Ca2+efflux. However, this effect was not specific, since K+also stimulated efflux. In contrast, an increase in osmotic pressure by addition of sucrose did not significantly stimulate Ca2+efflux. The results were consistent with H+and monovalent cations competing with Ca2+for a non-selective ion influx channel. Ca2+entry and efflux in chaA and yrbG knockouts were not significantly different from wild type, confirming that neither ChaA nor YrbG appear to play a major role in regulating cytosolic Ca2+in Escherichia coli. The number of Ca2+ions calculated to move per cell per second ranged from <1 to 100, depending on conditions. Yet a single eukaryote Ca2+channel, conductance 100 pS, should conduct >6 million ions per second. This raises fundamental questions about the nature and regulation of Ca2+transport in bacteria, and other small living systems such as mitochondria, requiring a new mathematical approach to describe such ion movements. The results have important significance in the adaptation of E. coli to different ionic environments such as the gut, fresh water and in sea water near sewage effluents.
影响因子：
2.9
作者：
LUTSENKO, S;KAPLAN, JH
通讯作者：
KAPLAN, JH
细菌钙转运。
DOI：
10.1016/0304-4157(87)90007-4
发表时间：
1987
期刊：
Biochimica et biophysica acta
影响因子：
--
作者：
Rosen,BP
通讯作者：
Rosen,BP