Graduate School of Life and Environmental Science, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Anim Sci J. 2009 Apr;80(2):193-7. doi: 10.1111/j.1740-0929.2008.00613.x.
The composition of tropomyosin (TPM) and myosin heavy chain (MyHC) isoforms was analyzed in 10 physiologically different bovine muscles (masseter, diaphragm, tongue, semispinalis, pectoralis profundus, biceps femoris, psoas major, semimembranosus, longissimus thoracis and semitendinosus) to clarify the relationships between TPM and MyHC isoforms in different muscle fiber types. The content of TPM1 and TPM3 was different in muscles according to their function in muscle contraction, although the content of TPM2 was constantly about 50% of the total TPM in all muscles. The content of TPM1 was higher in semimembranosus, longissimus thoracis and semitendinosus, while that of TPM3 was higher in masseter and diaphragm. The high positive correlation between MyHC-slow content and TPM3 content (r = 0.92) suggested a coexpression of TPM3 and MyHC-slow isoforms in a muscle fiber. MyHC-slow and TPM3 were expressed at the same level in masseter and diaphragm, whereas there was more TPM3 than MyHC-slow in tongue and semispinalis, so it appears that the excess TPM3 in tongue and semispinalis is expressed with other MyHC isoforms. MyHC-2a was the only fast type isoform expressed in tongue and semispinalis. Therefore, the excess TPM3 was composed of myofibrils with MyHC-2a. The results suggested that a fiber expressing MyHC-2a would be regulated delicately by changing the TPM isoform types.
本研究分析了 10 种生理上不同的牛肌肉（咀嚼肌、横膈膜、舌、半棘肌、胸深肌、股二头肌、腰大肌、半腱肌、最长肌和半膜肌）中肌球蛋白重链（MyHC）同工型和原肌球蛋白（TPM）的组成，以阐明不同肌纤维类型中 TPM 和 MyHC 同工型之间的关系。尽管 TPM2 在所有肌肉中的总 TPM 含量约为 50%，但根据肌肉在肌肉收缩中的功能，TPM1 和 TPM3 在肌肉中的含量有所不同。TPM1 在半腱肌、最长肌和半膜肌中的含量较高，而 TPM3 在咀嚼肌和横膈膜中的含量较高。MyHC-慢型含量与 TPM3 含量之间存在高度正相关（r = 0.92），这表明 TPM3 和 MyHC-慢型同工型在肌纤维中共同表达。在咀嚼肌和横膈膜中，MyHC-慢型和 TPM3 的表达水平相同，而在舌和半棘肌中，TPM3 比 MyHC-慢型多，因此舌和半棘肌中多余的 TPM3 似乎与其他 MyHC 同工型一起表达。MyHC-2a 是舌和半棘肌中唯一表达的快型同工型。因此，多余的 TPM3 由含有 MyHC-2a 的肌原纤维组成。结果表明，表达 MyHC-2a 的纤维可以通过改变 TPM 同工型来进行精细调节。
