Page 158 - The Miracle of Protein

156 THE MIRACLE OF PROTEIN

Motor proteins, also known as molecular motors, have the

potential of converting the chemical energy obtained by the
food we consume, into kinetic energy. In other words, they op-
erate just like the fueled gasoline engines we are so familiar
with. The work uses the following principle:
Motor proteins assume new forms by using the energy re-
leased after the last phosphate bond of the ATP molecule

(adenosine triphosphate) is cleaved. This energy-dependent
form change also helps to transform the position and shapes of
different structures inside the cell that are bound to these pro-
teins. In other words, phosphate changes, due to the protein’s
unique structure, creates propelling power for the protein.

No motor produced with today’s state of the art technolo-
gy can be either as small or as efficient as these protein motors.
Motor proteins are of different types, depending on their struc-
tures, the molecules they bind to, and the tasks they assume.
Microtubules -the highways of the cell city- are hollow
cylinders made up of tubulin proteins. Motor proteins that are

attached to the microtubules and walk on them are called ki-
nesin. Kinesins are proteins that use chemical energy to move (a
mechanochemical property), and play a role in converting the
chemical energy in ATP into kinetic energy. Kinesins, the mo-
tor proteins with their 100 different types, are made up of

around 340-350 amino acids. The kinesins, which were first
discovered in the large nerve cells of cuttlefish, walks to the (+)
end of the microtubules to transport the organelles and other
substances inside the cell. Every kinesin molecule has two legs
and can walk for 8 nm for every ATP that is hydrolyzed. 67