Regulatory interaction of sodium channel IQ-motif with calmodulin C-terminal lobe.
Regulatory interaction of sodium channel IQ-motif with calmodulin C-terminal lobe.
复制标题
DOI：
10.1016/s0006-291x(03)01183-5
复制
发表时间：
2003-07
影响因子：
3.1
通讯作者：
M. Mori;T. Konno;T. Morii;K. Nagayama;K. Imoto
中科院分区：
文献类型：
--
作者：
M. Mori;T. Konno;T. Morii;K. Nagayama;K. Imoto
越来越多的离子通道被发现直接与钙调素（CaM）结合，但其结构特征尚不清楚。以前，我们确定了钙调素的电压门控钠通道通过IQ基序序列的钙依赖性和非依赖性的相互作用。在这项研究中，我们使用胰蛋白酶消化的CaM片段（TR 1C和TR 2C）来分析Ca 2 +-CaM或无Ca 2+（apo）CaM与钠通道衍生的IQ基序肽（NaIQ）的结合。圆二色性光谱表明，NaIQ肽增强了CaM C-末端叶的α-螺旋度，但在不存在Ca 2+的情况下不增强CaM N-末端叶的α-螺旋度，而在存在Ca 2+的情况下，NaIQ增强了N-和C-末端叶的α-螺旋度。此外，竞争性结合实验表明，Ca 2+依赖的CaM结合的目标肽（MLCKp或蜂毒肽）与CaM显着抑制NaIQ。结果表明，IQ基序序列有助于防止靶蛋白在低Ca 2+浓度下活化，并可能解释为什么高度Ca 2+敏感的靶蛋白在细胞质中不被活化的调节机制。
An increasing number of ion channels have been found to be regulated by the direct binding of calmodulin (CaM), but its structural features are mostly unknown. Previously, we identified the Ca2+-dependent and -independent interactions of CaM to the voltage-gated sodium channel via an IQ-motif sequence. In this study we used the trypsin-digested CaM fragments (TR1C and TR2C) to analyze the binding of Ca2+-CaM or Ca2+-free (apo) CaM with a sodium channel-derived IQ-motif peptide (NaIQ). Circular dichroic spectra showed that NaIQ peptide enhanced α-helicity of the CaM C-terminal lobe, but not that of the CaM N-terminal lobe in the absence of Ca2+, whereas NaIQ enhanced the α-helicity of both the N- and C-terminal lobes in the presence of Ca2+. Furthermore, the competitive binding experiment demonstrated that Ca2+-dependent CaM binding of target peptides (MLCKp or melittin) with CaM was markedly suppressed by NaIQ. The results suggest that IQ-motif sequences contribute to prevent target proteins from activation at low Ca2+concentrations and may explain a regulatory mechanism why highly Ca2+-sensitive target proteins are not activated in the cytoplasm.