Center for Cancer Research, National Cancer Institute , National Institutes of Health , Frederick , Maryland 20892 , United States.
Department of Laboratory Medicine , National Institutes of Health , Bethesda , Maryland 20892 , United States.
Biochemistry. 2019 Dec 10;58(49):4903-4911. doi: 10.1021/acs.biochem.9b00854. Epub 2019 Nov 26.
IQ domain GTPase-activating scaffolding protein 1 (IQGAP1) mediates cytoskeleton, cell migration, proliferation, and apoptosis events. Calmodulin (CaM) modulates IQGAP1 functions by binding to its four tandem IQ motifs. Exactly how CaM binds the IQ motifs and which functions of IQGAP1 CaM regulates and how are fundamental mechanistic questions. We combine experimental pull-down assays, mutational data, and molecular dynamics simulations to understand the IQ-CaM complexes with and without Ca at the atomic level. Apo-CaM favors the IQ3 and IQ4 motifs but not the IQ1 and IQ2 motifs that lack two hydrophobic residues for interactions with apo-CaM's hydrophobic pocket. Ca-CaM binds all four IQ motifs, with both N- and C-lobes tightly wrapped around each motif. Ca promotes IQ-CaM interactions and increases the amount of IQGAP1-loaded CaM for IQGAP1-mediated signaling. Collectively, we describe IQ-CaM binding in atomistic detail and feature the emergence of Ca as a key modulator of the CaM-IQGAP1 interactions.
智商域 GTP 酶激活支架蛋白 1（IQGAP1）介导细胞骨架、细胞迁移、增殖和凋亡事件。钙调蛋白（CaM）通过与 IQGAP1 的四个串联 IQ 基序结合来调节 IQGAP1 的功能。CaM 如何结合 IQ 基序以及 CaM 调节 IQGAP1 的哪些功能以及如何调节是基本的机制问题。我们结合实验下拉测定、突变数据和分子动力学模拟，从原子水平上了解具有和不具有 Ca 的 IQ-CaM 复合物。apo-CaM 有利于 IQ3 和 IQ4 基序，但不利于 IQ1 和 IQ2 基序，因为它们缺乏与 apo-CaM 的疏水性口袋相互作用的两个疏水性残基。Ca-CaM 结合所有四个 IQ 基序，其 N-和 C-结构域紧密包裹每个基序。Ca 促进 IQ-CaM 相互作用，并增加 IQGAP1 介导信号转导时加载的 CaM 的量。总的来说，我们以原子细节描述了 IQ-CaM 结合，并以 Ca 作为 CaM-IQGAP1 相互作用的关键调节剂的出现为特征。
