Ionic regulation of MscK, a mechanosensitive channel from Escherichia coli
Ionic regulation of MscK, a mechanosensitive channel from Escherichia coli
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DOI：
10.1093/emboj/cdf537
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发表时间：
2002-10-15
期刊：
影响因子：
11.4
通讯作者：
Blount, P
中科院分区：
文献类型：
--
作者：
Li, YZ;Moe, PC;Blount, P
在大肠杆菌中已鉴定出形成独立的机械敏感通道活性的三种基因产物。其中两个，MscL 和 MScS，在使细胞耐受急性低渗应激方面发挥着至关重要的作用。对于第三种蛋白质 MscK (KefA)，人们知之甚少。在这里，我们表征了 MscK 通道活性，并将其与其结构和功能同源物 MScS 的活性进行比较。虽然两者都表现出轻微的阴离子偏好，但 MScK 似乎对膜张力更敏感。此外，MscK（而非MscS）活性似乎受外部离子环境调节，不仅需要膜张力，还需要高浓度的外部K+、NH4+、Rb+或Cs+来门控； Na+、Li+ 或 N-甲基-D-葡萄糖胺 (NMDG) 没有观察到活性。 MscK 功能获得突变体在存在 K+ 或类似离子的情况下自发门控，并且在存在 Na+、Li+ 和 NMDG 的情况下门控，但仅在受到膜张力刺激时才门控。 MscK 的敏感性增加和高度调节的性质表明其比其他细菌机械敏感通道具有更专门的生理作用。
Three gene products that form independent mechanosensitive channel activities have been identified in Escherichia coli. Two of these, MscL and MscS, play a vital role in allowing the cell to survive acute hypotonic stress. Much less is known of the third protein, MscK (KefA). Here, we characterize the MscK channel activity and compare it with the activity of its structural and functional homologue, MscS. While both show a slight anionic preference, MscK appears to be more sensitive to membrane tension. In addition, MscK, but not MscS activity appears to be regulated by external ionic environment, requiring not only membrane tension but also high concentrations of external K+, NH4+, Rb+ or Cs+ to gate; no activity is observed with Na+, Li+ or N-methyl-D-glucamine (NMDG). An MscK gain-of-function mutant gates spontaneously in the presence of K+ or similar ions, and will gate in the presence of Na+, Li+ and NMDG, but only when stimulated by membrane tension. Increased sensitivity and the highly regulated nature of MscK suggest a more specialized physiological role than other bacterial mechanosensitive channels.