Takano-Ohmuro H, Goldfine S M, Kojima T, Obinata T, Fischman D A
Department of Cell Biology and Anatomy, Cornell University Medical College, N.Y. 10021.
J Muscle Res Cell Motil. 1989 Oct;10(5):369-78. doi: 10.1007/BF01758433.
C-protein is an abundant protein, of unknown function, found in the striated muscles of all vertebrates (Offer et al., 1973). Based on differences in size, charge, antigenicity and sarcomere distribution, at least three different isoforms of this protein have been identified (Callaway & Bechtel, 1981; Yamamoto & Moos, 1983; Reinach et al., 1982; Dhoot et al., 1985). These have been termed fast-, slow- and cardiac-type isoforms, relative to their distribution in adult striated muscles. Each of these isoforms appears to be expressed sequentially during the development of the chicken pectoralis muscle (Obinata et al., 1984; Obinata, 1985). To better characterize the various isoforms of C-protein, we have reexamined its in vivo expression during avian myogenesis using a combination of 1- and 2-dimensional gel electrophoresis, cell-free translation and immunoblotting procedures. In this manuscript we demonstrate for the first time that at least four major C-protein isoforms can be distinguished in adult chicken muscles. These include a fast-type isoform in the pectoralis (PECT) muscle (Cf), a slow-type isoform in the anterior latissimus dorsi (ALD) muscle (Cs3), a second slow-type isoform in the posterior latissimus dorsi (PLD) muscle (Cs4) and a cardiac-type in the ventricle (Cc). During embryonic development of the PECT muscle two additional isoforms can be resolved. These are both slow-type isoforms based on their reactivities with ALD66, a monoclonal antibody specific for adult slow-type C-protein. These latter isoforms have been termed Cs1 and Cs2. Several of the isoforms, particularly Cs1 ands Cs3, exhibit two or more spots of different charge but identical molecular weight on 2-D gels. This observation suggests the possibility that these isoforms are post-translationally modified and possibly phosphorylated. Our data show the C-protein family in avian striated muscles to be highly complex. Additional genetic analyses and primary sequence studies will be required to distinguish transcriptional from post-transcriptional variants.
C蛋白是一种在所有脊椎动物的横纹肌中都存在的丰富蛋白质，其功能未知（奥弗等人，1973年）。基于大小、电荷、抗原性和肌节分布的差异，已鉴定出该蛋白质至少三种不同的同工型（卡拉韦和贝克特尔，1981年；山本和穆斯，1983年；雷纳赫等人，1982年；杜特等人，1985年）。相对于它们在成年横纹肌中的分布，这些同工型分别被称为快肌型、慢肌型和心脏型同工型。在鸡胸肌发育过程中，这些同工型中的每一种似乎都是按顺序表达的（小畑等人，1984年；小畑，1985年）。为了更好地表征C蛋白的各种同工型，我们使用一维和二维凝胶电泳、无细胞翻译和免疫印迹程序相结合的方法，重新研究了其在鸟类肌生成过程中的体内表达。在本论文中，我们首次证明在成年鸡肌肉中至少可以区分出四种主要的C蛋白同工型。这些包括胸肌（PECT）中的快肌型同工型（Cf）、背阔肌前部（ALD）中的慢肌型同工型（Cs3）、背阔肌后部（PLD）中的第二种慢肌型同工型（Cs4）以及心室中的心脏型同工型（Cc）。在PECT肌的胚胎发育过程中，可以分辨出另外两种同工型。基于它们与ALD66（一种对成年慢肌型C蛋白特异的单克隆抗体）的反应性，这两种都是慢肌型同工型。后一种同工型被称为Cs1和Cs2。几种同工型，特别是Cs1和Cs3，在二维凝胶上显示出两个或更多电荷不同但分子量相同的斑点。这一观察结果表明这些同工型可能在翻译后被修饰，并且可能被磷酸化。我们的数据表明鸟类横纹肌中的C蛋白家族非常复杂。需要进一步的遗传分析和一级序列研究来区分转录变体和转录后变体。
