Final answer:
The actin-binding protein that decreases cytoplasmic viscosity by severing actin filaments is known as a severing protein. Proteins such as gelsolin and cofilin are examples that can cut the filaments, affecting the cytoplasm's mechanical properties and enabling cellular processes like motility.
Step-by-step explanation:
The actin-binding protein known to decrease cytoplasmic viscosity by breaking existing actin filaments into two or more pieces is known as a severing protein. Actin filaments are a component of the cytoskeleton and are made of two intertwined strands of globular actin protein. Their assembly and disassembly are vital for various cellular processes, including muscle contraction and cell motility. Severing proteins like gelsolin and cofilin (not directly mentioned in the reference information but relevant to the topic) regulate the length of actin filaments by severing them, which can decrease the viscosity of the cytoplasm, allowing for improved cellular dynamics and motility.
Microfilaments, the narrowest of the three types of protein fibers in the cytoskeleton, are crucial for maintaining cell shape and enabling movement. They exhibit a viscoelastic property, contributing to the overall viscosity of cytoplasm in cells. Actin-myosin interactions, particularly in the presence of ATP, show that these proteins can dynamically alter their associations, further influencing the viscosity and mechanical properties of the cytoplasm.