Kinesin protein walking on microtubule

Its chemistry, when the Adenosine Triphosphate (ATP) binds to an active site on the leg protein (an active site is a part of a protein that has specific shape and electrical charge to fit a specific substrate eg. 

the ATP) it causes the proteins secondary or tertiary structure to change shape due to the ATP causing a conformational change when it releases the energy stored in its high energy phosphate groups (it causes the way the proteins peptide backbone's side chains interact with eachother to change, thus making it move).

This isn't random, due to the chemical properties of the peptide backbone's sidechains (functional groups), the protein can only change shape in specific ways. 

Now, to go along with the moving "foot" protein unit, the microtubule that it walks on has a specific chemical property (based off its structure) that allows the "foot" protein to temporarily bind it it and thus walk along it.

https://www.reddit.com/r/gifs/comments/12aiov/animation_of_kinesin_a_type_of_motor_protein_that/