Higher plant myosin XI moves processively on actin with 35 nm steps at high velocity
Higher plant myosin XI moves processively on actin with 35 nm steps at high velocity
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DOI：
10.1093/emboj/cdg130
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发表时间：
2003-03-17
期刊：
影响因子：
11.4
通讯作者：
Oiwa, K
中科院分区：
文献类型：
--
作者：
Tominaga, M;Kojima, H;Oiwa, K
从藻类到被子植物的各种植物细胞中都存在高速细胞质流。我们的特点是机械和酶的性质的高等植物肌球蛋白纯化烟草亮黄-2细胞，负责细胞质流，具有175 kDa的重链和钙调蛋白轻链。序列分析表明，它是一个XI类肌球蛋白和二聚体，在每个重链的轻链结合结构域中具有6个IQ基序。电子显微镜证实了这些预测。我们测量了它的ATP酶的特性，在体外运动，并使用光学陷阱纳米测量，力和运动开发的个别肌球蛋白XI分子。单个肌球蛋白XI分子以7 μ m/s的速度沿沿着肌动蛋白以35 nm的步长向前移动，这是已知最快的进行性运动。通过肌动蛋白着陆速率测定证实了持续加工能力。平均最大力与0.5pN相似，小于肌球蛋白II。珠携带单个肌球蛋白XI分子的停留时间分析符合ATP酶动力学，ADP释放速率限制。这些结果表明，肌球蛋白XI是高度专业化的产生快速进行性运动伴随着低的力量。
High velocity cytoplasmic streaming is found in various plant cells from algae to angiosperms. We characterized mechanical and enzymatic properties of a higher plant myosin purified from tobacco bright yellow-2 cells, responsible for cytoplasmic streaming, having a 175 kDa heavy chain and calmodulin light chains. Sequence analysis shows it to be a class XI myosin and a dimer with six IQ motifs in the light chain-binding domains of each heavy chain. Electron microscopy confirmed these predictions. We measured its ATPase characteristics, in vitro motility and, using optical trap nanometry, forces and movement developed by individual myosin XI molecules. Single myosin XI molecules move processively along actin with 35 nm steps at 7 mum/s, the fastest known processive motion. Processivity was confirmed by actin landing rate assays. Mean maximal force was similar to0.5 pN, smaller than for myosin IIs. Dwell time analysis of beads carrying single myosin XI molecules fitted the ATPase kinetics, with ADP release being rate limiting. These results indicate that myosin XI is highly specialized for generation of fast processive movement with concomitantly low forces.