Higuchi H, Umazume Y
Biophys J. 1985 Jul;48(1):137-47. doi: 10.1016/S0006-3495(85)83767-X.
Localization of the parallel elastic components (PECs) in skinned muscle fibers was investigated by analyzing the change of the resting tension, which accompanies the dissociation of the A- and I-bands. The A-band was dissociated from both ends by increasing the concentration of KCl under relaxing conditions (0.09-0.54 M KCl, 4.0 mM MgATP, 1.0 mM Mg2+, 4.0 mM EGTA, pH 6.0-9.0, 20 degrees C). At sarcomere lengths greater than or equal to 3.5 microns, the length of the A-band was estimated by comparing the intensity of the first-order optical diffraction line with the results of model calculations. These results were supported by differential-interference microscopy and sodium dodecyl sulfate gel electrophoresis. It was shown that the resting tension decreased nearly in proportion to the residual length of the A-band. At sarcomere lengths less than or equal to 4.0 microns, the resting tension after the dissociation of the A-band was lowered to less than 10% of the initial value. On the other hand, at sarcomere lengths greater than or equal to 5.0 microns the resting tension after the dissociation of the A-band still showed approximately 35% of the initial value and did not change even after the I-band was dissociated by a solution containing KI. From these results, we propose that most of the PECs contributing to resting tension bind almost uniformly to the A-band and there are also PECs connecting Z-lines.
通过分析与A带和I带解离相关的静息张力变化，研究了去皮肌纤维中平行弹性成分（PEC）的定位。在松弛条件下（0.09 - 0.54 M KCl、4.0 mM MgATP、1.0 mM Mg²⁺、4.0 mM EGTA、pH 6.0 - 9.0、20℃），通过增加KCl浓度使A带从两端解离。在肌节长度大于或等于3.5微米时，通过将一级光学衍射线的强度与模型计算结果进行比较来估计A带的长度。这些结果得到了微分干涉显微镜和十二烷基硫酸钠凝胶电泳的支持。结果表明，静息张力几乎与A带的剩余长度成比例下降。在肌节长度小于或等于4.0微米时，A带解离后的静息张力降至初始值的10%以下。另一方面，在肌节长度大于或等于5.0微米时，A带解离后的静息张力仍显示约为初始值的35%，即使在I带被含KI的溶液解离后也没有变化。根据这些结果，我们提出，大多数对静息张力有贡献的PEC几乎均匀地与A带结合，并且也存在连接Z线的PEC。
