Beta tropomyosin (Tpm2) is demonstrated for the first time at the protein level in a fish species, using a combination of electrophoresis, mass spectrometric peptide mapping and end-group analysis. Tpm2 accounts for 50% of the total tropomyosin in slow trunk muscle of the adult Atlantic salmon as determined by quantitative carboxypeptidase digestion and is also present in the head and pectoral fin. It is absent in the fast skeletal (lighter-toned) trunk muscle, the most abundant muscle, which is composed solely of an alpha-fast (Tpm1) isoform. In contrast to the mammalian homologues, salmon Tpm2 migrates faster than salmon Tpm1 in the presence of anionic detergent. Other distinguishing characteristics are a reduced content of cysteine (one per chain) and tyrosine (five per chain) and a unique carboxyl-terminal region (residues 276-284). Two isoforms (paralogs) of alpha-slow tropomyosin (Tpm3) having different contents of methionine and histidine exist in slow trunk muscle indicating duplication of the TPM3 gene. Minor skeletal muscles, surveyed for the first time, contain a mix of at least two tropomyosins - Tpm2 (~ 50% of total) in pectoral fin, jaw and tongue and another isoform, either Tpm1 (pectoral fin) or alpha-1-like Tpm (jaw and tongue). Cheek muscle contains Tpm1 and alpha 1-like Tpm in varying proportion depending upon the section (light or dark). Of the two tropomyosins in tongue, Tpm2 displays comparatively weaker affinity for troponin-Sepharose. A feature of the major sarcomeric tropomyosins in Atlantic salmon is a pair of neighbouring glycines situated between residues 20-90.

中文翻译：

---

大西洋鲑Salmo salar中的β-原肌球蛋白（Tpm2）演示和α-慢原肌球蛋白基因（TPM3）复制。

结合电泳，质谱肽图分析和端基分析，首次在鱼类中以蛋白质水平证明了原肌球蛋白（Tpm2）。根据定量羧肽酶消化法的测定，TPM2占成年大西洋鲑缓慢躯干肌中原肌球蛋白总量的50％，并且还存在于头和胸鳍中。快速骨骼（较浅色调）的躯干肌肉中不存在这种肌肉，它是最丰富的肌肉，仅由α-fast（Tpm1）亚型组成。与哺乳动物同源物相反，在阴离子去污剂存在下，鲑鱼Tpm2的迁移速度比鲑鱼Tpm1快。其他区别特征是半胱氨酸（每条链一个）和酪氨酸（每条链五个）的含量降低，以及独特的羧基末端区域（残基276-284）。甲硫氨酸和组氨酸含量不同的α-慢原肌球蛋白（Tpm3）的两种同工型（旁系同源物）存在于慢干肌中，表明TPM3基因重复。首次调查的次要骨骼肌包含至少两种原肌球蛋白-胸鳍，颌骨和舌头中的Tpm2（约占总数的50％）以及另一种同种异构体，即Tpm1（胸鳍）或类似alpha-1的混合物Tpm（下巴和舌头）。脸颊肌肉含有不同比例的Tpm1和类似alpha 1的Tpm，具体取决于切片（亮或暗）。在舌头的两种原肌球蛋白中，TPM2对肌钙蛋白-琼脂糖的亲和力相对较弱。大西洋鲑鱼中主要的肌节原肌球蛋白的特征是位于残基20-90之间的一对相邻的甘氨酸。