Final answer:
Three major motor proteins are dynein, kinesin, and myosin. Dynein and kinesin move cargo along microtubules in cells, with dynein generally moving cargo toward the microtubule minus-end and kinesin moving it toward the plus-end. These proteins are vital for cellular transport, organelle organization, and motility.
Step-by-step explanation:
Intracellular movement along microtubules is critical for the distribution and organization of organelles and vesicles within eukaryotic cells. This task is carried out by motor proteins that utilize the energy from ATP hydrolysis to propel themselves and their cargo along the microtubules. Dynein, kinesin, and myosin are three major motor proteins that serve distinct roles in cellular transport and motility. Dynein and kinesin, in particular, are crucial for movement along microtubules. Dynein moves cargo towards the minus end of microtubules and is involved in the sliding movement of cilia and flagella. Kinesin typically moves cargo towards the plus-end of microtubules, transporting materials such as secretory vesicles to the cell periphery. Myosin, while traditionally associated with actin microfilaments in muscle contraction, also interacts with microtubules in some cases.
For example, vesicles containing neurotransmitters travel along axonal microtubules powered by kinesin, reaching the nerve terminals. Similarly, pigment vesicles in a chameleon's skin cells use kinesin and dynein to move along microtubules, enabling the skin to change color. Thus, these motor proteins are essential for a wide range of cellular activities, including vesicle transport, organelle placement, and the structural integrity of motile appendages like cilia and flagella.