Final answer:
A kinesin head is tightly bound to its cytoskeletal track in the absence of nucleotides. This is different from a myosin head, which detaches from actin upon ATP binding and repositions itself for a power stroke during muscle contraction.
Step-by-step explanation:
A kinesin head is known to be tightly bound to its cytoskeletal track when it is bound to no nucleotide. This tight binding occurs in the absence of nucleotide, which is a different conformation compared to when it has ATP, ADP, GTP, or GDP bound. The mechanism is an essential aspect of the function of kinesin, a motor protein involved in intracellular transport, as it moves along microtubules within the cell.
It contrasts with myosin, another motor protein that interacts with actin filaments in muscle contractions. The myosin head attaches to the binding site on actin, and ATP binding causes the myosin head to detach from the actin. The subsequent hydrolysis of ATP to ADP and inorganic phosphate (Pi) releases energy, which changes the angle of the myosin head into a cocked, high-energy position, ready for a power stroke within muscle contraction.