Horio S, Yamada T, Shimizu H, Ishikawa H
J Muscle Res Cell Motil. 1985 Dec;6(6):709-23. doi: 10.1007/BF00712238.
An experimental model was constructed to examine the possible fact that myosin oligomers take a part in smooth muscle contraction. Single fibres prepared from glycerinated rabbit skeletal muscle were emptied of myosin and then irrigated with purified chicken gizzard myosin. This was a good preparation in which to see the structural change of gizzard myosin and its interaction with actin filaments under the electron microscope. The structure of gizzard myosin was thoroughly changed by varying the concentration of free Mg2+ in the bathing solution. Myosin thick filaments were formed at the position of the A-band longitudinally bridging adjacent I-segments at high concentration of free Mg2+, while most of them disappeared from the A-band and some localized in the I-segment at low concentration of free Mg2+. When this preparation was induced to contract isometrically, it showed quite different sarcomere patterns at high and low concentrations of free Mg2+. Tensions developed by this preparation were of the same magnitude at high and low concentrations of free Mg2+, which were approximately 5% of that developed by glycerinated skeletal muscle fibres. The shortening of the prepared fibre in a contracting medium was almost the same at varying concentrations of free Mg2+. The relation between the structural organization and the contracting nature of the prepared fibre as the concentration of free Mg2+ was varied is discussed in this paper with respect to the significance of oligomeric myosin in smooth muscle contraction.
构建了一个实验模型，以研究肌球蛋白寡聚体参与平滑肌收缩的可能性。从甘油处理过的兔骨骼肌制备的单纤维被去除肌球蛋白，然后用纯化的鸡胗肌球蛋白进行灌注。这是一个很好的制备物，可在电子显微镜下观察鸡胗肌球蛋白的结构变化及其与肌动蛋白丝的相互作用。通过改变浴液中游离Mg2+的浓度，鸡胗肌球蛋白的结构发生了彻底改变。在高浓度游离Mg2+时，肌球蛋白粗丝在A带位置形成，纵向桥接相邻的I段，而在低浓度游离Mg2+时，它们大多从A带消失，一些定位于I段。当该制备物被诱导进行等长收缩时，在高浓度和低浓度游离Mg2+下显示出相当不同的肌节模式。该制备物在高浓度和低浓度游离Mg2+下产生的张力大小相同，约为甘油处理的骨骼肌纤维产生张力的5%。在不同浓度的游离Mg2+下，制备的纤维在收缩介质中的缩短几乎相同。本文讨论了随着游离Mg2+浓度的变化，制备的纤维的结构组织与收缩性质之间的关系，涉及寡聚肌球蛋白在平滑肌收缩中的意义。
