Tsutsui Yasutaka, Yoshio Maki, Oiwa Kazuhiro, Yamada Akira
Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan.
J Mol Biol. 2007 Jan 12;365(2):325-32. doi: 10.1016/j.jmb.2006.10.006. Epub 2006 Oct 6.
Catch muscles are found in some invertebrates which can maintain high passive tension with little energy expenditure for long periods after their active contraction. Twitchin in the catch muscles has the ability to facilitate the tight binding of thick filaments to thin filaments, which is the structural basis of the catch tension. We defined this ability as catchability and assessed the catchability of twitchins purified from striated muscles of an oyster (Crassostrea gigas) and a scallop (Mimachlamys nobilis), by using an in vitro catch assay where the binding of filaments could be directly visualized under a light microscope. We found that both twitchins had catchability, even though these muscles are not considered to be catch muscles in physiological experiments. In addition, these muscles contained water-soluble factors regulating the binding of the catch, probably protein kinase A and protein phosphatase 2B. These findings suggest that not only bivalve smooth muscles but also striated muscles have a system that regulates their relaxation rate through the catchability of twitchin, at least at the molecular level.
在一些无脊椎动物中发现了捕捉肌，它们在主动收缩后能够长时间以很少的能量消耗维持高被动张力。捕捉肌中的肌动蛋白结合蛋白具有促进粗肌丝与细肌丝紧密结合的能力，这是捕捉张力的结构基础。我们将这种能力定义为捕捉性，并通过体外捕捉试验评估从牡蛎（太平洋牡蛎）和扇贝（华贵栉孔扇贝）的横纹肌中纯化出的肌动蛋白结合蛋白的捕捉性，在该试验中，细丝的结合可以在光学显微镜下直接观察到。我们发现这两种肌动蛋白结合蛋白都具有捕捉性，尽管在生理实验中这些肌肉不被认为是捕捉肌。此外，这些肌肉含有调节捕捉结合的水溶性因子，可能是蛋白激酶A和蛋白磷酸酶2B。这些发现表明，至少在分子水平上，不仅双壳类平滑肌，而且横纹肌都有一个通过肌动蛋白结合蛋白的捕捉性来调节其松弛速率的系统。
