Nishikawa So, Homma Kazuaki, Komori Yasunori, Iwaki Mitsuhiro, Wazawa Tetsuichi, Hikikoshi Iwane Atsuko, Saito Junya, Ikebe Reiko, Katayama Eisaku, Yanagida Toshio, Ikebe Mitsuo
Single Molecule Process Project, ICORP, JST, 2-4-14, Senba-Higashi, Mino, Osaka 562-0035, Japan.
Biochem Biophys Res Commun. 2002 Jan 11;290(1):311-7. doi: 10.1006/bbrc.2001.6142.
Among a superfamily of myosin, class VI myosin moves actin filaments backwards. Here we show that myosin VI moves processively on actin filaments backwards with large ( approximately 36 nm) steps, nevertheless it has an extremely short neck domain. Myosin V also moves processively with large ( approximately 36 nm) steps and it is believed that myosin V strides along the actin helical repeat with its elongated neck domain that is critical for its processive movement with large steps. Myosin VI having a short neck cannot take this scenario. We found by electron microscopy that myosin VI cooperatively binds to an actin filament at approximately 36 nm intervals in the presence of ATP, raising a hypothesis that the binding of myosin VI evokes "hot spots" on actin filaments that attract myosin heads. Myosin VI may step on these "hot spots" on actin filaments in every helical pitch, thus producing processive movement with 36 nm steps.
在肌球蛋白超家族中，VI类肌球蛋白使肌动蛋白丝向后移动。我们在此表明，VI类肌球蛋白在肌动蛋白丝上以大（约36纳米）步长向后进行持续移动，然而它具有极短的颈部结构域。V类肌球蛋白也以大（约36纳米）步长进行持续移动，并且据信V类肌球蛋白沿着肌动蛋白螺旋重复序列大步迈进，其伸长的颈部结构域对其大步长的持续移动至关重要。具有短颈部的VI类肌球蛋白无法采用这种情况。我们通过电子显微镜发现，在ATP存在的情况下，VI类肌球蛋白以大约36纳米的间隔协同结合到肌动蛋白丝上，从而提出一个假设，即VI类肌球蛋白的结合在肌动蛋白丝上引发“热点”，吸引肌球蛋白头部。VI类肌球蛋白可能在每个螺旋间距内踩在肌动蛋白丝上的这些“热点”上，从而产生36纳米步长的持续移动。
