Chi J C, Rubinstein N, Strahs K, Holtzer H
J Cell Biol. 1975 Dec;67(3):523-37. doi: 10.1083/jcb.67.3.523.
The weight ratio of myosin/actin, the myosin heavy chain content as the percentage of total protein (wt/wt), and the kinds of myosin light chains were determined in (a) standard muscle cultures, (b) pure myotube cultures, and (c) fibroblast cultures. Cells for these cultures were obtained from the breast of 11-day chick embryos. Standard cultures contain, in addition to myotubes, large numbers of replicating mononucleated cells. By killing these replicating cells with cytosine arabinoside, pure myotube cultures were obtained. The myosin/actin ratio (wt/wt) for pure myotube, standard muscle, and fibroblast cultures average 3.1, 1.9, and 1.1 respectively. By day 7, myosin in myotube cultures represents a minimum of 7% of the total protein, but about 3% in standard cultures and less than 1.5% in fibroblasts cultures. Myosin from standard cultures contains light chain LC1, LC2, and LC3, with a relative stoichiometry of the molarity of 1.0:1.9:0.5 and mol wt of 25,000, 18,000 and 16,000 daltons, identical to those in adult fast muscle. Myosin from pure myotubes exhibits light chains LC1 and LC2, with a molar ratio of 1.5:1.6. Myosin from fibroblast cultures possesses two light chains with a stoichiometry of 1.8:1.8 and mol wt of 20,000 and 16,000 daltons. Clearly, the faster migrating light chain, LC3, found in standard cultures is synthesized not by the myotubes but ty the mononucleated cells. In myotubes, both the assembly of the sarcomeres and the interaction between thick and thin filaments required for spontaneous contraction occur in the absence of light chain LC3. One set of structural genes for the myosin light and heavy chains appears to be active in mononucleated cells, whereas another set appears to be active in multinucleated myotubes.
在以下三种培养物中测定了肌球蛋白/肌动蛋白的重量比、肌球蛋白重链含量占总蛋白的百分比（重量/重量）以及肌球蛋白轻链的种类：(a) 标准肌肉培养物、(b) 纯肌管培养物和 (c) 成纤维细胞培养物。这些培养物的细胞取自 11 日龄鸡胚的胸部。标准培养物除了含有肌管外，还含有大量正在复制的单核细胞。通过用阿糖胞苷杀死这些正在复制的细胞，获得了纯肌管培养物。纯肌管、标准肌肉和成纤维细胞培养物的肌球蛋白/肌动蛋白比（重量/重量）分别平均为 3.1、1.9 和 1.1。到第 7 天，肌管培养物中的肌球蛋白占总蛋白的比例至少为 7%，但在标准培养物中约为 3%，在成纤维细胞培养物中则不到 1.5%。标准培养物中的肌球蛋白含有轻链 LC1、LC2 和 LC3，其相对化学计量摩尔比为 1.0:1.9:0.5，分子量分别为 25,000、18,000 和 16,000 道尔顿，与成年快肌中的相同。纯肌管中的肌球蛋白显示出轻链 LC1 和 LC2，摩尔比为 1.5:1.6。成纤维细胞培养物中的肌球蛋白有两条轻链，化学计量比为 1.8:1.8，分子量为 20,000 和 16,000 道尔顿。显然，在标准培养物中发现的迁移速度较快的轻链 LC3 不是由肌管合成的，而是由单核细胞合成的。在肌管中，肌节的组装以及自发收缩所需的粗、细肌丝之间的相互作用在没有轻链 LC3 的情况下也会发生。肌球蛋白轻链和重链的一组结构基因似乎在单核细胞中活跃，而另一组似乎在多核肌管中活跃。
