Ebisawa K, Nonomura Y
J Biochem. 1985 Oct;98(4):1127-30. doi: 10.1093/oxfordjournals.jbchem.a135361.
A Ca2+-dependent actin-severing 84K Mr protein prepared from bovine aorta caused four-fold activation of smooth muscle actin-activated myosin ATPase at a 1/10(2) molar ratio to actin in the presence of tropomyosin and light chain kinase-calmodulin in a Ca2+-dependent manner, while it inhibited it markedly at a 1/5 molar ratio. Purified actin-tropomyosin filaments under the experimental ATPase conditions were distributed in a range of more than 10 micron in length and the addition of the 84K Mr protein changed the filament length to around 1 micron at a 1/10(2) molar ratio to actin or less than 50 nm at a 1/5 molar ratio in the presence of Ca2+. However, the apparent length of actin filaments alone does not appear to be responsible for the activation of ATPase activity, since in the absence of tropomyosin, the ATPase activation was much less in spite of actin filament length changes. These results indicate the possibility that the 84K Mr protein plays an important role with tropomyosin in at least in vitro smooth muscle actin-myosin interaction.
从牛主动脉制备的一种依赖钙离子的肌动蛋白切断蛋白（分子量84K），在原肌球蛋白以及轻链激酶 - 钙调蛋白存在的情况下，以钙离子依赖的方式，在与肌动蛋白的摩尔比为1/10²时，能使平滑肌肌动蛋白激活的肌球蛋白ATP酶活性提高四倍，而在摩尔比为1/5时则显著抑制该酶活性。在实验性ATP酶条件下，纯化的肌动蛋白 - 原肌球蛋白丝长度分布在10微米以上，加入分子量84K的蛋白后，在钙离子存在的情况下，当与肌动蛋白的摩尔比为1/10²时，丝长度变为约1微米，当摩尔比为1/5时，丝长度小于50纳米。然而，单独的肌动蛋白丝的表观长度似乎并非ATP酶活性激活的原因，因为在没有原肌球蛋白的情况下，尽管肌动蛋白丝长度发生了变化，但ATP酶的激活程度要小得多。这些结果表明，分子量84K的蛋白至少在体外平滑肌肌动蛋白 - 肌球蛋白相互作用中与原肌球蛋白共同发挥重要作用。
