Montarras D, Fiszman M Y, Gros F
J Biol Chem. 1981 Apr 25;256(8):4081-6.
Tropomyosin, present in various types of chick embryo muscle, has been characterized by two-dimensional gel electrophoresis. In skeletal muscle, it was found that both the alpha and beta subunits exist as two variants, alpha 1, alpha 2 and beta 1, beta 2. The most acidic variants (alpha 2 and beta 2) could be demonstrated to be phosphorylated and, based upon the facts that 1) after phosphatase treatment alpha 2 and beta 2 co-migrate with alpha 1 and beta 1 and 2) in vitro translation of skeletal muscle mRNA produces only alpha 1 and beta 1, we suggest that alpha 2 and beta 2 merely represent the phosphorylated forms of alpha 1 and beta 1. A similar situation is found in differentiated muscle cultures in vitro. In cardiac muscle or in cardiocytes, in culture, the only subunit of tropomyosin which is present (the alpha subunit) is also phosphorylated. However, in smooth muscle, none of the tropomyosin subunits is phosphorylated. The use of various modifications in the second dimension of two-dimensional gel electrophoresis has allowed us to separate completely the alpha subunits of slow and fast muscle tropomyosin and to show that: 1) the cardiac alpha subunit is distinct from either the slow alpha or the fast alpha subunit and 2) in vitro differentiated cells synthesize a tropomyosin which, by co-migration under various conditions, is identical with fast muscle tropomyosin.
原肌球蛋白存在于多种类型的鸡胚肌肉中，已通过二维凝胶电泳进行了表征。在骨骼肌中，发现α和β亚基均以两种变体形式存在，即α1、α2和β1、β2。最酸性的变体（α2和β2）可被证明是磷酸化的，基于以下事实：1）磷酸酶处理后，α2和β2与α1和β1共迁移；2）骨骼肌mRNA的体外翻译仅产生α1和β1，我们认为α2和β2仅仅代表α1和β1的磷酸化形式。在体外分化的肌肉培养物中也发现了类似情况。在心肌或培养的心肌细胞中，原肌球蛋白唯一存在的亚基（α亚基）也是磷酸化的。然而，在平滑肌中，原肌球蛋白的亚基均未磷酸化。在二维凝胶电泳的第二维中使用各种修饰方法，使我们能够完全分离慢肌和快肌原肌球蛋白的α亚基，并表明：1）心肌α亚基不同于慢肌α亚基或快肌α亚基；2）体外分化的细胞合成的原肌球蛋白，在各种条件下通过共迁移，与快肌原肌球蛋白相同。
