Opposing Intermolecular Tuning of Ca2+ Affinity for Calmodulin by Neurogranin and CaMKII Peptides.
Opposing Intermolecular Tuning of Ca2+ Affinity for Calmodulin by Neurogranin and CaMKII Peptides.
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Neurogranin 和 CaMKII 肽对钙调蛋白的 Ca2 亲和力进行相反的分子间调节。
DOI：
10.1016/j.bpj.2017.01.020
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发表时间：
2017
影响因子：
3.4
通讯作者：
Cheung,MargaretS
中科院分区：
文献类型：
--
作者：
Zhang,Pengzhi;Tripathi,Swarnendu;Trinh,Hoa;Cheung,MargaretS
我们研究了结合钙调素（CaM）的目标化合物的结构对钙（Ca 2+）的亲和力的影响，通过整合粗粒模型和非平衡物理的全原子模拟。我们专注于钙调素和两个特定的目标，钙/钙调素依赖性蛋白激酶II（CaMKII）和神经颗粒蛋白（Ng）之间的结合，因为它们都调节钙调素依赖的钙信号通路在神经元。实验表明，Ca 2 +/CaM（holoCaM）与CaMKII肽的结合亲和力比无Ca 2+的CaM（apoCaM）高得多; CaMKII肽与CaM的结合反过来增加了Ca 2+对CaM的亲和力。然而，在Ng肽（Ng 13 -49）中没有观察到这种相互关系，其以相同数量级的结合亲和力结合apoCaM或holoCaM。与全CaM-CaMKII肽不同，其结构可以通过晶体学确定，apoCaM-Ng 13 - 49的结构描述由于结合亲和力低而未知，因此我们通过匹配来自核磁共振实验的Ng 13 - 49结合时CaM化学位移的变化来计算产生apoCaM-Ng 13 - 49结构的系综。接下来，我们使用Jarzynski等式计算了原子模型中有和没有结合靶点的Ca 2+对CaM亲和力的变化。我们发现Ng 13 - 49存在时Ca 2+对CaM亲和力降低的分子基础是通过显示Ng肽的N-末端酸性区域打开Ca 2+结合环之间的β-折叠结构，特别是在CaM的C-结构域，使得Ca 2+释放。相反，CaMKII肽通过稳定两个Ca 2+结合环来增加Ca 2+对CaM的C结构域的亲和力。我们推测apoCaM-Ng 13 - 49和holoCaM-CaMKII结合复合物中的独特结构差异描绘了CaM的渐进靶向结合机制对其Ca 2+结合亲和力的重要性。
We investigated the impact of bound calmodulin (CaM)-target compound structure on the affinity of calcium (Ca2+) by integrating coarse-grained models and all-atomistic simulations with nonequilibrium physics. We focused on binding between CaM and two specific targets, Ca2+/CaM-dependent protein kinase II (CaMKII) and neurogranin (Ng), as they both regulate CaM-dependent Ca2+signaling pathways in neurons. It was shown experimentally that Ca2+/CaM (holoCaM) binds to the CaMKII peptide with overwhelmingly higher affinity than Ca2+-free CaM (apoCaM); the binding of CaMKII peptide to CaM in return increases the Ca2+affinity for CaM. However, this reciprocal relation was not observed in the Ng peptide (Ng13–49), which binds to apoCaM or holoCaM with binding affinities of the same order of magnitude. Unlike the holoCaM-CaMKII peptide, whose structure can be determined by crystallography, the structural description of the apoCaM-Ng13–49is unknown due to low binding affinity, therefore we computationally generated an ensemble of apoCaM-Ng13–49structures by matching the changes in the chemical shifts of CaM upon Ng13–49binding from nuclear magnetic resonance experiments. Next, we computed the changes in Ca2+affinity for CaM with and without binding targets in atomistic models using Jarzynski's equality. We discovered the molecular underpinnings of lowered affinity of Ca2+for CaM in the presence of Ng13–49by showing that the N-terminal acidic region of Ng peptide pries open theβ-sheet structure between the Ca2+binding loops particularly at C-domain of CaM, enabling Ca2+release. In contrast, CaMKII peptide increases Ca2+affinity for the C-domain of CaM by stabilizing the two Ca2+binding loops. We speculate that the distinctive structural difference in the bound complexes of apoCaM-Ng13–49and holoCaM-CaMKII delineates the importance of CaM's progressive mechanism of target binding on its Ca2+binding affinities.