MAGNESIUM TRANSPORT IN SALMONELLA-TYPHIMURIUM - CHARACTERIZATION OF MAGNESIUM INFLUX AND CLONING OF A TRANSPORT GENE
MAGNESIUM TRANSPORT IN SALMONELLA-TYPHIMURIUM - CHARACTERIZATION OF MAGNESIUM INFLUX AND CLONING OF A TRANSPORT GENE
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DOI：
10.1128/jb.168.3.1444-1450.1986
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发表时间：
1986-12-01
影响因子：
3.2
通讯作者：
MAGUIRE, ME
中科院分区：
文献类型：
--
作者：
HMIEL, SP;SNAVELY, MD;MAGUIRE, ME
采用动力学和遗传学相结合的方法研究了镁离子在鼠伤寒沙门氏菌LT-2中的内流。在高浓度的硫酸镁(10 MM)中生长的野生型细胞的Km下降到3µm，而在低浓度的硫酸镁(10µm)中生长后的Vmax增加了60%。Co2+是高浓度生长的细胞中镁离子内流的简单竞争性抑制物(Ki=30微米)，但在低浓度生长的细胞中仅阻断部分镁离子的内流。CO2+内流表现出与镁离子内流相似的动力学(Km=30µm；Vmax=每108个细胞每分钟0.5nmolCO2+)，但不受生长条件的影响。Mg2+和Mn2+对CO2+内流均有竞争性抑制作用。通过对Co2+毒害水平的自发抗性的选择，分离出了影响镁吸收的突变。其中一类突变体CORA在84min附近定位，基因顺序如下：CORA、METE、ZIE-3161：：Tn10、PepQ。第二类标记为CORB，位于PYRB附近98分钟处。在所有生长条件下，当被CorA突变完全消除时，CorA突变株中的镁离子内流(相对于野生型)减少。携带来自大肠杆菌K-12或鼠伤寒沙门氏菌的CORA区域的重组质粒补充了鼠伤寒沙门氏菌的CORA突变，恢复了对Co2+和Mg2+的吸收，并赋予了对Co2+的敏感性。鼠伤寒沙门氏菌CorA基因定位于约1.5kb的限制性片段。
The influx of Mg2+ in Salmonella typhimurium LT-2 was studied by both kinetic and genetic techniques. Wild-type cells grown in a high MgSO4 concentration (10 mM) exhibited a Km decreased to 3 .mu.M, and the Vmax increased 60% after growth in a low MgSO4 concentration (10 .mu.M). Co2+ was a simple competitive inhibitor (Ki = 30 .mu.M) of Mg2+ influx in cells grown in high Mg2+ concentrations but blocked only a portion of the Mg2+ influx in cells grown in low Mg2+ concentrations. Co2+ influx exhibited kinetics similar to those of Mg2+ influx (Km = 30 .mu.M; Vmax = 0.5 nmol of Co2+ per min per 108 cells) but not affected by growth conditions. Co2+ influx was competitively inhibited by both Mg2+ and Mn2+. Mutations affecting Mg2+ uptake were isolated by selection for spontaneous resistance to toxic levels of Co2+. One class of mutants designed corA mapped at 84 min near metE with the following gene order: corA, metE, zie-3161::Tn10, pepQ. A second class designated corB mapped at 98 min near pyrB. Mg2+ influx was decreased in a corA mutant strain (relative to that of the wild type) when completely abolished by the corA mutation under all growth conditions. Recombinant plasmids carrying the corA region from either Escherichia coli K-12 or S. typhimurium complemented the corA mutation in S. typhimurium, restoring uptake of both Co2+ and Mg2+ and conferring sensitivity to Co2+. The S. typhimurium corA gene was localized to a restriction fragment of approximately 1.5 kilobases.