Electron tomography of fast frozen, stretched rigor fibers reveals elastic distortions in the myosin crossbridges
Electron tomography of fast frozen, stretched rigor fibers reveals elastic distortions in the myosin crossbridges
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DOI：
10.1016/j.jsb.2004.03.008
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发表时间：
2004-09-01
影响因子：
3
通讯作者：
Taylor, KA
中科院分区：
文献类型：
--
作者：
Liu, J;Reedy, MC;Taylor, KA
作为第一步冻结捕获和3-D建模的非常快速的负载引起的结构反应的活性肌球蛋白头，我们探讨了较长的持续力依赖性变化的构象范围内的昆虫飞行肌肉（IFM）的僵硬性横桥。在1 - 2%的斜坡拉伸（1000 ms）后将僵硬的IFM纤维急速冷冻并冷冻取代。从Araldite嵌入的纤维的30 nm纵向截面的倾斜系列计算断层图像。修改程序的对齐和对应分析分组的自相似的crossbridge形式到16类平均值与4.5 nm的分辨率，揭示肌动蛋白原体和肌球蛋白S2段的一些crossbridge的第一次在肌肉薄切片。手动拟合到横桥密度的Acto-S1原子模型需要一系列杠杆臂调整，以匹配扭曲的严格横桥。与低张力僵直相比，一些杠杆臂没有变化，而另一些杠杆臂则弯曲并向M方向移位高达4.5 nm。平均位移为1.6 +/-1.0 nm。用其类平均值替换每个非平均的39 nm横桥基序的"映射回"图像显示了沿着沿着116 nm重复序列分布的扭曲和未改变的横桥的有序混合，这反映了甚至在拉伸之前僵硬肌球蛋白头部负载的差异。(C)2004年爱思唯尔公司All rights reserved.
As a first step toward freeze-trapping and 3-D modeling of the very rapid load-induced structural responses of active myosin heads, we explored the conformational range of longer lasting force-dependent changes in rigor crossbridges of insect flight muscle (IFM). Rigor IFM fibers were slam-frozen after ramp stretch (1000 ms) of 1-2% and freeze-substituted. Tomograms were calculated from tilt series of 30 nm longitudinal sections of Araldite-embedded fibers. Modified procedures of alignment and correspondence analysis grouped self-similar crossbridge forms into 16 class averages with 4.5 nm resolution, revealing actin protomers and myosin S2 segments of some crossbridges for the first time in muscle thin sections. Acto-S1 atomic models manually fitted to crossbridge density required a range of lever arm adjustments to match variably distorted rigor crossbridges. Some lever arms were unchanged compared with low tension rigor, while others were bent and displaced M-ward by up to 4.5 nm. The average displacement was 1.6 +/- 1.0 nm. "Map back" images that replaced each unaveraged 39 nm crossbridge motif by its class average showed an ordered mix of distorted and unaltered crossbridges distributed along the 116 nm repeat that reflects differences in rigor myosin head loading even before stretch. (C) 2004 Elsevier Inc. All rights reserved.