INTERACTION OF INVERTEBRATE MYOSINS WITH ACTIN

在滑动肌动蛋白体外运动试验中， 荧光标记的肌动蛋白覆盖在肌球蛋白表面， 在荧光显微镜下。在迄今报告的所有案件中， 下面的肌球蛋白表面不能直接可视化。通常假设 结合的肌球蛋白丝或单体是随机取向的。我们有 分离大的天然粗丝从软体动物肌肉使用快速 温和的方法。这些粗丝的长度在10到50微米之间 这取决于肌肉的来源，并且可以直接在 使用视频增强微分干涉对比度的玻璃表面 显微镜这使我们能够直接关联的运动， 荧光标记的肌动蛋白丝与它们在天然的 双极粗灯丝我们的观察表明肌动蛋白可以 朝向和远离粗灯丝的中心， 肌动蛋白决定运动的方向。肌动蛋白丝运动 向粗灯丝中心的运动速度大约是 那些远离中心的人肌动蛋白离开细胞膜的运动 粗灯丝的中心与通常发生在 肌肉收缩，并建议肌球蛋白的头部必须非常 灵活.

In the sliding actin in vitro motility assay, the movement of fluorescently-labeled actin over a surface coated with myosin is visualized in the fluorescent microscope. In all the cases reported to date, the underlying myosin surface is not directly visualized. It is usually assumed that the bound myosin filaments or monomers are randomly oriented. We have isolated large native thick filaments from molluscan muscle using a rapid and gentle method. These thick filaments are between 10 and 50 um long depending on the source of the muscle and can be directly visualized on the glass surface using video-enhanced differential interference contrast microscopy. This allows us to directly correlate the movement of the fluorescently-labeled actin filaments with their position on the native bipolar thick filament. Our observations show that actin can travel both toward and away from the center of the thick filament and that the polarity of actin determines the direction of movement. Actin filaments moving toward the center of the thick filament travel about 9 times faster than those traveling away from the center. The movement of actin away from the center of the thick filament is opposite that which usually occurs in muscle contraction and suggest that the heads of myosin must be very flexible.