Studies on the regulatory mechanism of myofibril assembly

1.肌原纤维发生过程中肌动蛋白组装的调控在鸡胚的背肌中发现了大量的未聚合肌动蛋白。我们成功地纯化了三个肌动蛋白结合蛋白的16 kDa，19 kDa和20 kDa，分别调节肌动蛋白组装在胚胎骨骼肌。非肌肉型肌动蛋白和横纹肌肌动蛋白在胚胎肌肉中共表达。16 kDa的蛋白被鉴定为广泛分布于非肌肉细胞中的profilin。它对-，-肌动蛋白比对-肌动蛋白具有更高的亲和力，从而抑制了它们在胚胎肌肉中的特异性组装。19 kDa蛋白与鸡脑中发现的ADF相似，而20 kDa蛋白与cofilin相似。无论肌动蛋白的类型，这两种蛋白质抑制肌动蛋白聚合，但肌球蛋白的抑制作用被删除。我们的结论是，在发育中的肌肉肌动蛋白组装增强的抑制蛋白的数量减少，肌球蛋白的数量增加和肌动蛋白的类型的变化。微管在肌肉形成中的作用我们通过免疫细胞化学方法证明微管构成了细胞骨架元件，它在发育过程中对肌管的伸长起主要作用.发育中肌肉结构蛋白的鉴定对胚胎肌肉中的C蛋白和肌钙蛋白T进行了鉴定。利用基因技术测定了在胚胎骨骼肌中瞬时表达的胚胎肌球蛋白轻链（L23）的一级结构，并用特异性单克隆抗体观察了其在肌丝中的组装。

1. Regulation of Actin Assembly during Myofibrillogeneses A large amount of unpolymrized actin was detected in the skelctal muscle of young chicken embryos. We succeeded in purifying three actin-binding proteins of 16 kDa, 19 kDa and 20 kDa, respectively, which regulate actin assembly in the embryonic skeletal muscle. -and -actins of non-muscle type and -striated muscle actin are co-expressed in the embryonic muscle. The 16 kDa protein was identified with profilin which is widely distributed in non-muscle cells. It exhibited higher affinity to -, -actins than to -actin to inhibit speci-fically their assembly in the embryonic muscle. The 19 kDa protein identified with ADF which was discovered in chicken brain, while the 20 kDa protein resembled cofilin. Both proteins inhibited actin polymerization regardless of the type of actin, but the inhibitory action was removed by myosin. We conclude that actin assembly in developing muscle is enhanced by decrease in the amount of the inhibitory proteins, increase in myosin amount and the change in the type of actin.2. Role of Microtubules in Muscle Formation We demonstrated that microtubles make up the cytoskeletal element which is most responsible for elongation of myotubes during development by immunocytochemistry.3. Characterization of Muscle Structural Proteins in Developing Muscle C-protein and troponin T in embryonic muscle were characterized. The primary structure of embryonic mysoin light chain (L23) which is transiently expressed in embryonic skeletal muscle was determined by gene technology and its assembly in myofilaments was visualized with a specific monoclonal antibody.