A conserved arginine near the filter of Kir1.1 controls Rb/K selectivity.
A conserved arginine near the filter of Kir1.1 controls Rb/K selectivity.
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DOI：
10.4161/chan.4.3.11982
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发表时间：
2010-05
期刊：
影响因子：
--
通讯作者：
Walters DE
中科院分区：
文献类型：
--
作者：
Sackin H;Nanazashvili M;Li H;Palmer LG;Walters DE
ROMK(Kir1.1)通道在哺乳动物肾单位的集合管、连接小管和粗大的上肢中对钾的分泌和循环具有重要作用。我们在控制Rb/K选择性的选择性过滤器附近的通道的P环中发现了一个高度保守的Arg。此Arg突变为Tyr(R128Y-Kir1.1b，R147Y-Kir1.1a)使宏观电导比Grb/GK增加了17±3倍，并将wt-Kir1.1中NH4>；K&Gt；TL&Gt；Rb≫Cs的选择性顺序改变为R128Y中的：Rb>；Cs>；TL>；NH4≫K，而Kir1.1的高K/Na渗透率没有显著变化。R128M的Rb、Tl、NH4和Cs电导相对于K的增加相似，但幅度较小。R128Y仍然容易被外部BA和蜜蜂毒素TPNQ阻断，尽管R128Y对TPNQ的亲和力低于野生型。R128Y-Kir1.1b对GRb/GK比值的影响可以部分解释为该突变体的单道Rb电导(12.4±0.5ps)大于K电导(<；1.5ps)。在-120 mV，以Rb为导通的R128Y门控动力学与wt-Kir1.1导通Rb的动力学相似，但具有更长的开放时间(129ms vs.6ms)和两个闭合状态(13ms，905ms)，导致开放概率(Po)为0.5，而wt-Kir1.1导通Rb的Po为0.9，在-120 mV时，其单一闭合状态为1ms。单通道R128Y整流在切除的、由内向外的贴片中消除，并使用对称的RB溶液。Rb/K电导比的大幅增加，而K/Na渗透率或整流没有变化，这与R128Y-Kir1.1b一致，可能是由于破坏了过滤器附近的亚基内盐桥(R128-e118)，导致了选择性过滤器的细微变化。
ROMK (Kir1.1) channels are important for K secretion and recycling in the collecting duct, connecting tubule and thick ascending limb of the mammalian nephron. We have identified a highly conserved Arg in the P loop of the channel near the selectivity filter that controls Rb/K selectivity. Mutation of this Arg to a Tyr (R128Y-Kir1.1b, R147Y-Kir1.1a) increased the macroscopic conductance ratio, GRb/GK by 17 ± 3 fold and altered the selectivity sequence from NH4 > K > Tl > Rb ≫ Cs in wt-Kir1.1 to: Rb > Cs > Tl > NH4 ≫ K in R128Y, without significant change in the high K/Na permeability ratio of Kir1.1. R128M produced similar, but smaller, increases in Rb, Tl, NH4 and Cs conductance relative to K. R128Y remained susceptible to block by both external Ba and the honeybee toxin, TPNQ, although R128Y had a reduced affinity for TPNQ, relative to wild-type. The effect of R128Y-Kir1.1b on the GRb/GK ratio can be partly explained by a larger single-channel Rb conductance (12.4 ± 0.5 pS) than K conductance (<1.5 pS) in this mutant. The kinetics of R128Y gating at -120 mV with Rb as the permeantion were similar to those of wt-Kir1.1 conducting Rb, but with a longer open time (129 ms vs. 6 ms for wt) and two closed states (13 ms, 905 ms), resulting in an open probability (Po) of 0.5, compared to a Po of 0.9 for wt-Kir1.1, which had a single closed state of 1 ms at -120 mV. single-channel R128Y rectification was eliminated in excised, inside-out patches with symmetrical Rb solutions. The large increase in the Rb/K conductance ratio, with no change in K/Na permeability or rectification, is consistent with R128Y-Kir1.1b causing a subtle change in the selectivity filter, perhaps by disruption of an intra-subunit salt bridge (R128-e118) near the filter.
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影响因子：
3.8
作者：
Choe, H;Sackin, H;Palmer, LG
通讯作者：
Palmer, LG
影响因子：
56.9
作者：
Doyle, DA;Cabral, JM;MacKinnon, R
通讯作者：
MacKinnon, R
DOI：
10.1073/pnas.94.4.1568
发表时间：
1997-02-18
影响因子：
11.1
作者：
Yang, J;Yu, M;Jan, LY
通讯作者：
Jan, LY
DOI：
10.1152/ajpcell.1996.271.6.c1949
发表时间：
1996-12-01
影响因子：
5.5
作者：
Zhou, H;Chepilko, S;Sackin, H
通讯作者：
Sackin, H
影响因子：
3.4
作者：
Sackin, H;Nanazashvili, M;Walters, DE
通讯作者：
Walters, DE