Final answer:
Dynein is a motor protein that moves towards the minus end of microtubules and is responsible for retrograde vesicle transport and the motility of cilia and flagella.
Step-by-step explanation:
The dynein motor protein moves in the direction towards the minus end of microtubules. In cells, dynein powers the retrograde movement of vesicles, such as neurotransmitter vesicles, which travel back to the cell body of neurons after releasing their contents at the nerve endings. This action is in contrast to kinesin, another motor protein, which moves vesicles towards the plus end of microtubules during anterograde transport. Dynein is also involved in the bending movements of cilia and flagella due to its role in causing microtubules to slide relative to each other.