Biphasic Ca2+-dependent switching in a calmodulin-IQ domain complex
Biphasic Ca2+-dependent switching in a calmodulin-IQ domain complex
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DOI：
10.1021/bi052533w
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发表时间：
2006-06-06
期刊：
影响因子：
2.9
通讯作者：
Persechini, Anthony
中科院分区：
文献类型：
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作者：
Black, D. J.;Leonard, Jared;Persechini, Anthony
游离Ca ~（2+）浓度与钙调素（CaM）和神经调节素IQ结构域复合物的表观解离常数之间的关系包括两个阶段。在第一阶段，结合到CaM中的C-ter EF手对的Ca 2+使复合物的Kd从无Ca 2+的值2.3 +/- 0.1 μ M增加到14.4 +/- 1.3 μ M的值。在第二阶段，钙离子结合到N-端EF手对减少的K-D为复杂的值为2.5 +/- 0.1 μ M，逆转的第一阶段的效果。由于与这些相相关的能量偶联效应，Ca 2+与C-ter EF手对结合的平均解离常数增加了约3倍，从1.8 ± 0.1 μ M增加到5.1 ± 0.7 μ M，Ca 2+与N-ter EF手对结合的平均解离常数降低了相同的因子，从11.2 +/- 1.0到3.5 +/- 0.6 μ M。这些特性产生的复合物的表观解离常数和游离Ca 2+浓度之间的钟形关系，与上升和下降阶段的中点之间的距离为5-6 μ M。因此，从神经调节蛋白IQ结构域释放钙调素似乎是促进在一个相对狭窄的范围内的游离钙离子浓度。我们的研究结果表明，CaM-IQ结构域复合物可以作为双相Ca 2+开关，通过相反的效果，Ca 2+绑定顺序的两个EF手对CaM。
The relationship between the free Ca2+ concentration and the apparent dissociation constant for the complex between calmodulin (CaM) and the neuromodulin IQ domain consists of two phases. In the first phase, Ca2+ bound to the C-ter EF hand pair in CaM increases the K-d for the complex from the Ca2+-free value of 2.3 +/- 0.1 mu M to a value of 14.4 +/- 1.3 mu M. In the second phase, Ca2+ bound to the N-ter EF hand pair reduces the K-d for the complex to a value of 2.5 +/- 0.1 mu M, reversing the effect of the first phase. Due to energy coupling effects associated with these phases, the mean dissociation constant for binding of Ca2+ to the C-ter EF hand pair is increased similar to 3-fold, from 1.8 +/- 0.1 to 5.1 +/- 0.7 mu M, and the mean dissociation constant for binding of Ca2+ to the N-ter EF hand pair is decreased by the same factor, from 11.2 +/- 1.0 to 3.5 +/- 0.6 mu M. These characteristics produce a bell-shaped relationship between the apparent dissociation constant for the complex and the free Ca2+ concentration, with a distance of 5-6 mu M between the midpoints of the rising and falling phases. Release of CaM from the neuromodulin IQ domain therefore appears to be promoted over a relatively narrow range of free Ca2+ concentrations. Our results demonstrate that CaM-IQ domain complexes can function as biphasic Ca2+ switches through opposing effects of Ca2+ bound sequentially to the two EF hand pairs in CaM.