Ca2+ and Mg2+ modulate conformational dynamics and stability of downstream regulatory element antagonist modulator
Ca2+ and Mg2+ modulate conformational dynamics and stability of downstream regulatory element antagonist modulator
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DOI：
10.1002/pro.2646
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发表时间：
2015-05-01
期刊：
影响因子：
8
通讯作者：
Miksovska, Jaroslava
中科院分区：
文献类型：
--
作者：
Khoa Pham;Dhulipala, Gangadhar;Miksovska, Jaroslava
下游调节元件拮抗剂调节剂（DREAM）属于神经元钙传感器（NCS）家族，其将细胞内Ca 2+浓度的变化转化为多种反应，包括基因表达、Kv通道活性的调节和钙稳态。尽管与其他NCS成员的序列和结构的显着相似性，DREAM显示了NCS中独特的几个功能，如在脱辅基状态下形成四聚体，并与各种细胞内生物大分子，包括DNA，早老素，Kv通道和钙调蛋白的相互作用。在这里，我们使用光谱技术结合分子动力学模拟来研究Ca 2 +/Mg 2+协会DREAM诱导的构象变化。我们的数据表明，一个微小的影响，Ca 2+协会的N-和C-末端结构域的整体结构，虽然Ca 2+结合降低了构象的异质性，明显的荧光寿命分布在Ca 2+结合形式的蛋白质的减少。时间分辨荧光数据表明，Ca（2+）结合触发的构象转变，其特征在于更有效的淬灭色氨酸残基。DREAM的解折叠通过部分解折叠的中间体发生，该中间体通过与EF-手3和EF-手4的Ca 2+结合而稳定。天然状态相对于部分未折叠状态仅在Ca 2+和Mg 2+存在下稳定，这表明在生理条件下，无Ca 2+的DREAM表现出高的构象灵活性，这可能有助于其生理功能。
Downstream Regulatory Element Antagonist Modulator (DREAM) belongs to the family of neuronal calcium sensors (NCS) that transduce the intracellular changes in Ca2+ concentration into a variety of responses including gene expression, regulation of Kv channel activity, and calcium homeostasis. Despite the significant sequence and structural similarities with other NCS members, DREAM shows several features unique among NCS such as formation of a tetramer in the apo-state, and interactions with various intracellular biomacromolecules including DNA, presenilin, Kv channels, and calmodulin. Here we use spectroscopic techniques in combination with molecular dynamics simulation to study conformational changes induced by Ca2+/Mg2+ association to DREAM. Our data indicate a minor impact of Ca2+ association on the overall structure of the N- and C-terminal domains, although Ca2+ binding decreases the conformational heterogeneity as evident from the decrease in the fluorescence lifetime distribution in the Ca2+ bound forms of the protein. Time-resolved fluorescence data indicate that Ca(2+)binding triggers a conformational transition that is characterized by more efficient quenching of Trp residue. The unfolding of DREAM occurs through an partially unfolded intermediate that is stabilized by Ca2+ association to EF-hand 3 and EF-hand 4. The native state is stabilized with respect to the partially unfolded state only in the presence of both Ca2+ and Mg2+ suggesting that, under physiological conditions, Ca2+ free DREAM exhibits a high conformational flexibility that may facilitate its physiological functions.