One of the most important processes in our cells is the transport of molecules from one part of the cell, for example from the protein producing factories around the nucleus, to another, such as the cell membrane if that protein needs to be excreted by the cell.
Therefore, an organised system of filaments and transporters exists to mediate the movement of proteins and cellular components across the cell.
Kinesin molecules can be seen as the cargo trains of cells and the microtubule filaments as their rails. At one end, the green portion at the top of the image on the left, the molecule binds to its cargo, while at the other it attaches to the microtubule tracks.
The end attached to the microtubule contains a molecular motor, which utilises the common currency of the cell, the energy-producing ATP molecule, to pull itself across the microtubule, which can be seen as remarkably similar to a walking mechanism (albeit with a bit of artistic license!):
This system is elegantly intricate. Kinesins are designed to only travel in one direction along microtubules. They make the most of the fact that microtubules are intrinsically charged, with a positive end at the edge of the cell and a negative end at their site of origin, typically near the nucleus at the centre. Therefore, kinesins are specialised to move cellular components towards the outside of the cell and hence their major function is in the distribution of newly-synthesised cellular components, such as mitochondria and ribosomes to their required location.
‘Til next time…