Identification of the activation gate of HERG K^+ channel

HERG K^通道激活门的识别

基本信息

批准号：
14370028
负责人：
ISHII Kuniaki
金额：
$ 8.06万
依托单位：
Yamagata University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14370028/
关键词：
HERG voltage sensor activation gate outward currents inward currents ion selectivity charged amino acids 第6膜貫通領域

项目摘要

1. Wild type HERG K^+ channel opens upon depolarization and does not open upon hyperpolarization. We have found that a point mutation at I655 on the S6 makes the HERG channel open upon hyperpolarization. Further mutagenesis analyses showed that substitution of I655 with charged or polar amino acid residues resulted in the similar change (The resultant mutants opened upon hyperpolarization). On the other hand, HERG K^+ channel seemed to require hydrophobic residues at 655 to open upon depolarization like the wild type channel.2. Similar but not identical results were obtained with point mutations of G657 on the S6. When charged residues (except glutamatic acid) or polar residues were present at 657, the mutant channels opened upon hyperpolarization. In the case of the residue at 657, HERG K^+ channel seemed to require a small residue such as alanine or serine at 657 to open upon depolarization.3. Selectivity for K^+ ion was lost in the I655 and G657 mutant channels that open upon hyperpolarization. Although the mechanism is not known, opening of the mutant channels upon hyperpolarization seemed to involve the movement of the ion selectivity filter.4. When the three charged residues on the S4-S5 linker of HERG WT channel were neutralized, upon hyperpolarization, obvious inward currents flowing through the mutant channel were observed, in addition to outward currents on depolarization. However, the neutralization of the charged residues did not cause any change in the I655 and G657 mutants that open upon hyperpolarization.5. It has been reported that the inner helices bend at the glycine hinge, when K^+ channel opens. Substitution of the corresponding glycine in HERG with alanine suggested that the glycine hinge is involved in the opening of the WT HERG channel, but not in the I655 and G657 mutant channels.

1。野生型HERG K^+通道在去极化后打开，并且在超极化后不打开。我们发现，S6上I655处的点突变使HERG通道在超极化后打开。进一步的诱变分析表明，用带电或极性氨基酸残基的I655取代导致相似的变化（在超极化后开放的突变体）。另一方面，HERG K^+通道似乎需要655处的疏水残基在去极化时打开，例如野生型通道2。 S6上使用G657的点突变获得了相似但不是相同的结果。当带电的残基（除谷氨酸除外）或极性残基在657时，突变通道在超极化后打开。在657处的残留物的情况下，HERG K^+通道似乎需要一个小残留物，例如657时的丙氨酸或丝氨酸才能在去极化时打开。3。在超极化时打开的I655和G657突变通道中，K^+离子的选择性丧失。尽管该机制尚不清楚，但超极化时突变通道的打开似乎涉及离子选择性滤波器的运动。4。当HERG WT通道的S4-S5连接器上的三个带电残基被中和时，在超极化后，除了去极化时向外电流外，还观察到明显的向内电流流过突变通道。然而，带电残基的中和不会导致在超极化后打开的I655和G657突变体的任何变化。5。据报道，当K^+通道打开时，内螺旋在甘氨酸铰链处弯曲。用丙氨酸在HERG中取代相应的甘氨酸表明甘氨酸铰链参与WT HERG通道的开放，但在I655和G657突变通道中不参与。