Dependence of thick filament structure in relaxed mammalian skeletal muscle on temperature and interfilament spacing.
Dependence of thick filament structure in relaxed mammalian skeletal muscle on temperature and interfilament spacing.
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松弛的哺乳动物骨骼肌中粗肌丝结构对温度和肌丝间距的依赖性。
DOI：
10.1085/jgp.202012713
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发表时间：
2021-03-01
期刊：
影响因子：
--
通讯作者：
Brunello E
中科院分区：
文献类型：
--
作者：
Caremani M;Fusi L;Linari M;Reconditi M;Piazzesi G;Irving TC;Narayanan T;Irving M;Lombardi V;Brunello E
Caremani等人使用X射线衍射和干涉来表征松弛的去膜和完整的静息哺乳动物肌肉中的粗细丝的结构，揭示了两个紧密间隔的轴向周期性以及当细丝激活通过冷却到接近生理温度以下来模拟时发生的结构变化。骨骼肌的收缩受肌动蛋白的细丝和肌球蛋白的粗丝的结构变化的调节，但肌球蛋白为基础的调节是不太可能被保存后，粗丝隔离，其结构基础仍然很差的特点。在这里，我们描述的周期性特征的粗丝结构原位高分辨率小角度X射线衍射和干涉。我们使用松弛的脱膜纤维和静息的完整肌肉制备物来评估在脱膜纤维中是否保留了粗丝调节，这在以前的研究中已被广泛使用。我们发现，在两种制剂中的粗丝表现出两个紧密间隔的轴向周期，43.1 nm和45.5 nm，在近生理温度。较短的周期性与肌球蛋白螺旋相匹配，双极肌丝中两个肌球蛋白阵列之间的X射线干涉表明，肌丝的所有区域都遵循这种周期性。45.5-nm重复序列没有螺旋成分，起源于肌球蛋白层更接近与该区域的肌联蛋白超重复序列相关的肌丝中点。冷却放松或休息的肌肉，这部分模拟了钙激活对粗丝结构的影响，破坏了肌球蛋白马达的螺旋顺序，它们从细丝骨架中移出。用5%葡聚糖压缩脱膜纤维的细丝晶格，使细丝间间距恢复到完整肌肉中的间距，从而稳定高温结构。轴向周期性的长丝骨干增加冷却，但在晶格压缩纤维的周期性的肌球蛋白头不遵循的骨干的延伸。在近生理温度下，晶格压缩的脱膜纤维中的粗丝结构与完整的静息肌肉中的粗丝结构相似，这表明在这些条件下脱膜后，粗丝的天然结构在很大程度上得以保留，尽管在大多数先前研究中使用该制剂的条件下并不如此。
Caremani et al. use x-ray diffraction and interference to characterize the structure of thick filaments in relaxed demembranated and intact resting mammalian muscle, revealing two closely spaced axial periodicities as well as structural changes that occur when filament activation is mimicked by cooling below near-physiological temperature. Contraction of skeletal muscle is regulated by structural changes in both actin-containing thin filaments and myosin-containing thick filaments, but myosin-based regulation is unlikely to be preserved after thick filament isolation, and its structural basis remains poorly characterized. Here, we describe the periodic features of the thick filament structure in situ by high-resolution small-angle x-ray diffraction and interference. We used both relaxed demembranated fibers and resting intact muscle preparations to assess whether thick filament regulation is preserved in demembranated fibers, which have been widely used for previous studies. We show that the thick filaments in both preparations exhibit two closely spaced axial periodicities, 43.1 nm and 45.5 nm, at near-physiological temperature. The shorter periodicity matches that of the myosin helix, and x-ray interference between the two arrays of myosin in the bipolar filament shows that all zones of the filament follow this periodicity. The 45.5-nm repeat has no helical component and originates from myosin layers closer to the filament midpoint associated with the titin super-repeat in that region. Cooling relaxed or resting muscle, which partially mimics the effects of calcium activation on thick filament structure, disrupts the helical order of the myosin motors, and they move out from the filament backbone. Compression of the filament lattice of demembranated fibers by 5% Dextran, which restores interfilament spacing to that in intact muscle, stabilizes the higher-temperature structure. The axial periodicity of the filament backbone increases on cooling, but in lattice-compressed fibers the periodicity of the myosin heads does not follow the extension of the backbone. Thick filament structure in lattice-compressed demembranated fibers at near-physiological temperature is similar to that in intact resting muscle, suggesting that the native structure of the thick filament is largely preserved after demembranation in these conditions, although not in the conditions used for most previous studies with this preparation.
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影响因子：
5.6
作者：
HUXLEY, HE;BROWN, W
通讯作者：
BROWN, W
影响因子：
16.6
作者：
Fusi, L.;Brunello, E.;Yan, Z.;Irving, M.
通讯作者：
Irving, M.
影响因子：
2.7
作者：
BENNETT, P;CRAIG, R;OFFER, G
通讯作者：
OFFER, G
影响因子：
56.9
作者：
LABEIT, S;KOLMERER, B
通讯作者：
KOLMERER, B
DOI：
10.1073/pnas.97.13.7226
发表时间：
2000-06-20
影响因子：
11.1
作者：
Linari, M;Piazzesi, G;Lombardi, V
通讯作者：
Lombardi, V