Final answer:
Coat proteins are assisted by microtubule motor proteins (dynein and kinesin) and the microtubule network to transport vesicles to specific locations in the cell.
Step-by-step explanation:
In a cell, various coat proteins such as clathrin and COP are involved in the trafficking of vesicles to and from specific locations. Besides these proteins, microtubule motor proteins like dynein and kinesin also play critical roles. These motor proteins use ATP to move cargo, such as vesicles, through the cell. The vesicles bud off from the Rough Endoplasmic Reticulum (RER) with help from COPI and COPII coat proteins and then fuse with the cis face of the Golgi apparatus. As they pass through the Golgi, proteins undergo processing like glycosylation. Post-Golgi, the vesicles carrying the modified proteins attach to motor proteins and move along microtubules towards their destinations which could be within the cell or at the plasma membrane for secretion outside the cell.
Therefore, the 'two friends' that assist coat proteins in vesicle transportation are the microtubule motor proteins (dynein and kinesin) and the dynamic microtubule network they traverse.