Protruding masticatory (superfast) myosin heads from poorly aligned thick filaments of dog jaw muscle revealed by X-ray diffraction
Protruding masticatory (superfast) myosin heads from poorly aligned thick filaments of dog jaw muscle revealed by X-ray diffraction
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X 射线衍射显示，狗下巴肌肉排列不良的粗细丝中突出的咀嚼（超快）肌球蛋白头
DOI：
10.1093/jb/mvp143
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Y.
中科院分区：
文献类型：
--
作者：
Yamaguchi;M.;Takemori;S.;Kimura;M.;Tanishima;Y.;Nakayoshi;T.;Kimura;S.;Ohno;T.;Yagi;N.;Hoh;F.Y. J.;Umazume;Y.
为了表征表达咀嚼（超快）肌球蛋白的颌肌纤维的结构，将狗咬肌的甘油纤维的 X 射线衍射图与松弛状态下的狗胫骨前肌的 X 射线衍射图进行了比较。咬肌纤维的经向反射横向较宽，表明肌球蛋白丝沿丝轴交错。与胫骨前肌纤维相比，咬肌纤维第一肌球蛋白层线的峰值强度较低且偏向子午线，而在相似的肌节长度下，晶格间距较大。这些表明咀嚼纤维的肌球蛋白头是可移动的，并且倾向于从丝轴向肌动蛋白丝突出。降低温度或用N-苯基马来酰亚胺处理使胫骨前纤维第一肌球蛋白层线的峰值向子午线移动，所得轮廓类似于咬肌纤维的轮廓。这表明未经处理的咀嚼纤维中突出的移动头处于 ATP 结合状态。弱结合跨桥数量的增加可能有助于咀嚼纤维在收缩过程中的高比力。电子显微照片证实了咀嚼纤维肌节内粗肌丝沿着肌丝轴交错排列，这一特征可能在大范围的肌节长度上赋予有效的力发展。
To characterize the structure of jaw muscle fibres expressing masticatory (superfast) myosin, X-ray diffraction patterns of glycerinated fibres of dogmasseterwere compared with those of dogtibialis anteriorin the relaxed state. Meridional reflections ofmasseterfibres were laterally broad, indicating that myosin filaments are staggered along the filament axis. Compared withtibialis anteriorfibres, the peak of the first myosin layer line ofmasseterfibres was lower in intensity and shifted towards the meridian, while lattice spacings were larger at a similar sarcomere length. These suggest that the myosin heads of masticatory fibres are mobile, and tend to protrude from the filament shaft towards actin filaments. Lowering temperature or treating withN-phenylmaleimide shifted the peak of the first myosin layer line oftibialis anteriorfibres towards the meridian and the resulting profile resembled that ofmasseterfibres. This suggests that the protruding mobile heads in the non-treated masticatory fibres are in the ATP-bound state. The increased population of weakly binding cross-bridges may contribute towards the high specific force of masticatory fibres during contraction. Electron micrographs confirmed the staggered alignment of thick filaments along the filament axis within sarcomeres of masticatory fibres, a feature that may confer efficient force development over a wide range of the sarcomere lengths.