Calcium-induced mechanical change in the neck domain alters the activity of plant myosin XI.
Calcium-induced mechanical change in the neck domain alters the activity of plant myosin XI.
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DOI：
10.1074/jbc.m112.346668
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发表时间：
2012-08-31
期刊：
影响因子：
--
通讯作者：
Oiwa K
中科院分区：
文献类型：
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作者：
Tominaga M;Kojima H;Yokota E;Nakamori R;Anson M;Shimmen T;Oiwa K
背景：在植物细胞中，肌球蛋白XI驱动的细胞质流被Ca ~（2+）抑制。结果：通过Ca ~（2+）诱导的钙调素解离，单个肌球蛋白XI分子的颈长和步长减小。结论：植物肌球蛋白XI通过钙调蛋白的解离受到Ca 2+的调节，这是一种不同于脊椎动物肌球蛋白V的调节方式。意义：Ca 2+影响肌球蛋白XI的机械性质。植物肌球蛋白XI作为马达在植物细胞中产生细胞质流。虽然细胞质流是已知的，以调节细胞内钙离子浓度，这种控制的分子机制尚未完全理解。在这里，我们研究了肌球蛋白XI的调节机制，钙离子在分子水平上。肌动蛋白丝很容易脱离肌球蛋白XI在体外运动试验中，在高Ca 2+浓度（pCa 4）伴随着钙调蛋白轻链脱离颈部域。电子显微镜观察表明，肌球蛋白XI在pCa 4缩短了30%的颈部域。单分子分析表明，肌球蛋白XI在pCa 4时的步长在低负荷下缩短至27 nm，在高负荷下缩短至22 nm，而完整肌球蛋白XI的步长为35 nm，与负荷无关。这些结果表明，颈部域的机械性能的调制是一个关键因素，实现钙离子诱导的调节细胞质流动。
Background: Cytoplasmic streaming driven by myosin XI is inhibited by Ca2+ in plant cells. Results: The neck length and step size of a single myosin XI molecule decreased through Ca2+-induced calmodulin dissociation. Conclusion: Plant myosin XI is regulated by Ca2+ through dissociation of calmodulin, a different manner of regulation than for vertebrate myosin V. Significance: Ca2+ affects the mechanical properties of myosin XI. Plant myosin XI functions as a motor that generates cytoplasmic streaming in plant cells. Although cytoplasmic streaming is known to be regulated by intracellular Ca2+ concentration, the molecular mechanism underlying this control is not fully understood. Here, we investigated the mechanism of regulation of myosin XI by Ca2+ at the molecular level. Actin filaments were easily detached from myosin XI in an in vitro motility assay at high Ca2+ concentration (pCa 4) concomitant with the detachment of calmodulin light chains from the neck domains. Electron microscopic observations showed that myosin XI at pCa 4 shortened the neck domain by 30%. Single-molecule analysis revealed that the step size of myosin XI at pCa 4 was shortened to 27 nm under low load and to 22 nm under high load compared with 35 nm independent of the load for intact myosin XI. These results indicate that modulation of the mechanical properties of the neck domain is a key factor for achieving the Ca2+-induced regulation of cytoplasmic streaming.