Reedy M C, Reedy M K, Leonard K R, Bullard B
Department of Cell Biology, Duke University Medical Center, Durham, NC 27710.
J Mol Biol. 1994 May 27;239(1):52-67. doi: 10.1006/jmbi.1994.1350.
The position of the large troponin complex relative to myosin crossbridges in Lethocerus flight muscle (IFM) has been probed by electron microscopy (EM) using monoclonal antibodies against troponin T (TnT) and troponin H (TnH), a heavy troponin component found in several insect muscles. Infiltration of gold-tagged and plain Fab fragments into glycerinated IFM before fixation established in non-overlap fibers that the beads every 38.7 nm along thin filaments are troponin. Original and optically filtered EM images from 25 nm longitudinal and 15 nm cross-sections of partially overlapped fibers suggests that epitopes on both TnT and TnH are very close to the rear crossbridge of the rigor double chevron. When Fab was infiltrated into relaxed fibers and ATP was subsequently removed, the resulting rigor crossbridge lattice was disrupted by antibody labeling of the troponin. The results confirm that the lattice of rigor crossbridges and troponin are congruent and suggest that crossbridges may interact with troponin in IFM, possibly serving as a partial basis for the stretch activation characteristic of this muscle.
利用针对肌钙蛋白T（TnT）和肌钙蛋白H（TnH，一种在几种昆虫肌肉中发现的重肌钙蛋白成分）的单克隆抗体，通过电子显微镜（EM）对大肌钙蛋白复合物在大田鳖飞行肌（IFM）中相对于肌球蛋白横桥的位置进行了探测。在固定前将金标记和平板Fab片段渗入甘油化的IFM中，在非重叠纤维中确定沿着细肌丝每38.7 nm的珠状物是肌钙蛋白。来自部分重叠纤维的25 nm纵向和15 nm横截面的原始和光学滤波EM图像表明，TnT和TnH上的表位都非常靠近强直双V形后横桥。当Fab渗入松弛纤维并随后去除ATP时，产生的强直横桥晶格被肌钙蛋白的抗体标记破坏。结果证实强直横桥和肌钙蛋白的晶格是一致的，并表明横桥可能在IFM中与肌钙蛋白相互作用，这可能是该肌肉拉伸激活特性的部分基础。
