Measuring the influence of the BKCa {beta}1 subunit on Ca2+ binding to the BKCa channel.
Measuring the influence of the BKCa {beta}1 subunit on Ca2+ binding to the BKCa channel.
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DOI：
10.1085/jgp.200810129
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发表时间：
2009-02
影响因子：
3.8
通讯作者：
Cox, Daniel H.
中科院分区：
文献类型：
--
作者：
Sweet, Tara-Beth;Cox, Daniel H.
与脑和骨骼肌的BKCa通道相比，平滑肌的大电导Ca2+活化钾（BKCa）通道对Ca2+异常敏感。这是由于BKCa辅助亚基β1的组织特异性表达，其存在显著增加Ca2+促进通道打开的效力和功效。β1本身不包含Ca2+结合位点，因此它增加BKCa通道Ca2+敏感性的机制一直很有趣。先前，我们证明了β1可以稳定电压传感器的激活，因此当β1存在时，激活会在更负的电压下发生。这减少了Ca2+打开通道必须做的工作，从而增加了通道的表观Ca2+亲和力，而不改变通道Ca2+结合位点的实际亲和力。然而，为了解释β1对通道Ca2+敏感性的全部影响，我们还提出β1必须对Ca2+结合产生影响。在这里，为了验证这一假设，我们使用高分辨率的Ca2+剂量响应曲线和结合位点特异性突变来测量β1对Ca2+结合的影响。我们发现β1的共表达改变了BKCa通道的两种高亲和力Ca2+结合位点的Ca2+结合，主要是在通道打开时增加RCK1位点的亲和力，而在通道关闭时降低Ca2+碗位点的亲和力。这两种修饰都增加了开放和关闭之间的亲和力差异，因此当β1存在时，Ca2+在任何一个位点的结合对通道开放都有更大的影响。
The large-conductance Ca2+-activated potassium (BKCa) channel of smooth muscle is unusually sensitive to Ca2+ as compared with the BKCa channels of brain and skeletal muscle. This is due to the tissue-specific expression of the BKCa auxiliary subunit β1, whose presence dramatically increases both the potency and efficacy of Ca2+ in promoting channel opening. β1 contains no Ca2+ binding sites of its own, and thus the mechanism by which it increases the BKCa channel's Ca2+ sensitivity has been of some interest. Previously, we demonstrated that β1 stabilizes voltage sensor activation, such that activation occurs at more negative voltages with β1 present. This decreases the work that Ca2+ must do to open the channel and thereby increases the channel's apparent Ca2+ affinity without altering the real affinities of the channel's Ca2+ binding sites. To explain the full effect of β1 on the channel's Ca2+ sensitivity, however, we also proposed that there must be effects of β1 on Ca2+ binding. Here, to test this hypothesis, we have used high-resolution Ca2+ dose–response curves together with binding site–specific mutations to measure the effects of β1 on Ca2+ binding. We find that coexpression of β1 alters Ca2+ binding at both of the BKCa channel's two types of high-affinity Ca2+ binding sites, primarily increasing the affinity of the RCK1 sites when the channel is open and decreasing the affinity of the Ca2+ bowl sites when the channel is closed. Both of these modifications increase the difference in affinity between open and closed, such that Ca2+ binding at either site has a larger effect on channel opening when β1 is present.
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影响因子：
56.9
作者：
NELSON, MT;CHENG, H;LEDERER, WJ
通讯作者：
LEDERER, WJ
DOI：
10.1085/jgp.109.5.647
发表时间：
1997-05
期刊：
The Journal of general physiology
影响因子：
--
作者：
Cui J;Cox DH;Aldrich RW
通讯作者：
Aldrich RW
Ryanodine受体与大鼠脑动脉平滑肌细胞中的KCA通道的功能偶联。
影响因子：
3.8
作者：
Pérez, GJ;Bonev, AD;Patlak, JB;Nelson, MT
通讯作者：
Nelson, MT
影响因子：
20.1
作者：
Plüger, S;Faulhaber, J;Pongs, O
通讯作者：
Pongs, O
DOI：
10.1085/jgp.200409052
发表时间：
2004-05
期刊：
The Journal of general physiology
影响因子：
--
作者：
Bao L;Kaldany C;Holmstrand EC;Cox DH
通讯作者：
Cox DH