Final answer:
The tail of myosin II contributes to the structural assembly and stability of myosin filaments but does not have ATPase activity. The myosin head contains the active site for ATPase activity and interaction with actin, which is critical for muscle contraction. The tail's role is more organizational, aiding in the assembly of myosin into filaments.
Step-by-step explanation:
In the structure of myosin II, the myosin tail plays a crucial role in the assembly and stability of the myosin filaments. However, the ATPase activity and the interaction with actin, crucial for muscle contraction, are properties of the myosin head. The tail itself does not have ATPase activity, indicating that it does not directly engage in the energy conversion process responsible for muscle contraction. Upon ATP hydrolysis, it is the myosin head that undergoes a conformational change to a cocked position, storing the energy needed for the power stroke during muscle contraction.
Proteolytic enzymes can cleave myosin into two separate fragments: S1, which represents the head, and the tail. The S1 head fragment has been found to possess slow ATPase activity, which is significantly enhanced when the S1 fragment is mixed with actin. This interaction between the myosin head and actin is essential for the muscle fiber's ability to contract. The tail, by contrast, acts more as a structural component, contributing to the assembly of myosin into thick filaments which are necessary for muscle contraction but itself does not contribute to ATP hydrolysis. The myosin tail's role, therefore, is more supportive and organizational within the structure of myosin filaments.