Such filaments are usually composed of the contractile proteins actin and/or myosin, and are thought to play a role in cell motility, and perhaps also change in shape.

• 这种丝通常由伸缩蛋白肌动蛋白和（或）肌球蛋白组成，一般而言它们在细胞运动中起一定作用，并可能改变自身的形状。