Final answer:
Actin-binding proteins known as severing proteins bind to the side of actin filaments and break them into two, playing a role in remodeling the actin cytoskeleton for processes like muscle contraction and cell motility.
Step-by-step explanation:
The category of actin-binding proteins that bind to the side of an existing actin filament and break it into two is known as severing proteins. An example of such proteins is gelsolin, which severs actin filaments in response to changes in the concentration of calcium ions. The result of this severing action is the regulation of the length of actin filaments, which is crucial for various cellular processes.
This cutting action on filaments contributes to the dynamic remodeling of the actin cytoskeleton, which is essential for muscle contraction, cell division, and cell motility. Actin is involved in many cellular events, powered by ATP to assemble into a filamentous form, working with myosin in muscle contraction and cellular movements such as cytoplasmic streaming and amoeboid movement.