Myosin heavy-chain kinase A from Dictyostelium possesses a novel actin-binding domain that cross-links actin filaments.
Myosin heavy-chain kinase A from Dictyostelium possesses a novel actin-binding domain that cross-links actin filaments.
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来自盘基网柄菌的肌球蛋白重链激酶 A 拥有一种新型肌动蛋白结合结构域，可交联肌动蛋白丝。
DOI：
10.1042/bj20051376
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Steimle,PaulA
中科院分区：
文献类型：
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作者：
Russ,Misty;Croft,Daniel;Ali,Omar;Martinez,Raquel;Steimle,PaulA
肌球蛋白重链激酶A(MHCK A)通过肌球蛋白II重链磷酸化，催化Dictyostelium细胞内肌球蛋白II细丝的分解。MHCK A具有一个富含卷曲的结构域，该结构域介导了该激酶的寡聚化、细胞定位和肌动蛋白结合活性。F-肌动蛋白(丝状肌动蛋白)与螺旋卷曲结构域结合导致MHCK A活性增加40倍。在本研究中，我们研究了卷曲线圈结构域的肌动蛋白结合特性，以此作为识别MHCK A介导的肌球蛋白II细丝在细胞中被调控的机制的一种手段。共沉淀分析表明，MHCKA的盘绕结构域与F-肌动蛋白协同结合，KD约为0.5g/μM，化学计量比约为5：1[肌动蛋白/C(1-498)]。进一步的分析表明，卷曲结构域沿着肌动蛋白细丝的长度结合，并具有至少两个肌动蛋白结合区。令人惊讶的是，我们发现卷曲线圈结构域将肌动蛋白细丝交叉连接成束，这表明MHCK A可以通过两种重要方式影响细胞骨架：(1)通过肌球蛋白II重链磷酸化驱动肌球蛋白II-细丝的分解；(2)通过交联化/捆绑肌动蛋白细丝。这一发现与其他支持数据一起，提出了一种模型，在该模型中，MHCK A介导的肌动蛋白细丝捆绑在细胞中特定位置的激酶的募集和激活中发挥核心作用。最终，这为实现肌球蛋白II细丝的强大和高度局部化的破坏提供了一种手段，有助于在趋化、胞质分裂和多细胞发育等过程中促进细胞形状的极化变化。
Myosin heavy-chain kinase A (MHCK A) catalyses the disassembly of myosin II filaments inDictyosteliumcells via myosin II heavy-chain phosphorylation. MHCK A possesses a ‘coiled-coil’-enriched domain that mediates the oligomerization, cellular localization and actin-binding activities of the kinase. F-actin (filamentous actin) binding by the coiled-coil domain leads to a 40-fold increase in MHCK A activity. In the present study we examined the actin-binding characteristics of the coiled-coil domain as a means of identifying mechanisms by which MHCK A-mediated disassembly of myosin II filaments can be regulated in the cell. Co-sedimentation assays revealed that the coiled-coil domain of MHCK A binds co-operatively to F-actin with an apparentKDof approx. 0.5 μM and a stoichiometry of approx. 5:1 [actin/C(1–498)]. Further analyses indicate that the coiled-coil domain binds along the length of the actin filament and possesses at least two actin-binding regions. Quite surprisingly, we found that the coiled-coil domain cross-links actin filaments into bundles, indicating that MHCK A can affect the cytoskeleton in two important ways: (1) by driving myosin II-filament disassembly via myosin II heavy-chain phosphorylation, and (2) by cross-linking/bundling actin filaments. This discovery, along with other supporting data, suggests a model in which MHCK A-mediated bundling of actin filaments plays a central role in the recruitment and activation of the kinase at specific sites in the cell. Ultimately this provides a means for achieving the robust and highly localized disruption of myosin II filaments that facilitates polarized changes in cell shape during processes such as chemotaxis, cytokinesis and multicellular development.